[Release] Major improvements to generate contributors script

This commit introduces several major improvements to the script
that generates the contributors list for release notes, notably:

(1) Use release tags instead of a range of commits. Across branches,
commits are not actually strictly two-dimensional, and so it is not
sufficient to specify a start hash and an end hash. Otherwise, we
end up counting commits that were already merged in an older branch.

(2) Match PR numbers in addition to commit hashes. This is related
to the first point in that if a PR is already merged in an older
minor release tag, it should be filtered out here. This requires us
to do some intelligent regex parsing on the commit description in
addition to just relying on the GitHub API.

(3) Relax author validity check. The old code fails on a name that
has many middle names, for instance. The test was just too strict.

(4) Use GitHub authentication. This allows us to make far more
requests through the GitHub API than before (5000 as opposed to 60
per hour).

(5) Translate from Github username, not commit author name. This is
important because the commit author name is not always configured
correctly by the user. For instance, the username "falaki" used to
resolve to just "Hossein", which was treated as a github username
and translated to something else that is completely arbitrary.

(6) Add an option to use the untranslated name. If there is not
a satisfactory candidate to replace the untranslated name with,
at least allow the user to not translate it.
[Release] Cache known author translations locally

This bypasses unnecessary calls to the Github and JIRA API.
Additionally, having a local cache allows us to remember names
that we had to manually discover ourselves.
[SPARK-4798][SQL] A new set of Parquet testing API and test suites

This PR provides a set Parquet testing API (see trait `ParquetTest`) that enables developers to write more concise test cases. A new set of Parquet test suites built upon this API  are added and aim to replace the old `ParquetQuerySuite`. To avoid potential merge conflicts, old testing code are not removed yet. The following classes can be safely removed after most Parquet related PRs are handled:

- `ParquetQuerySuite`
- `ParquetTestData`

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Author: Cheng Lian <lian@databricks.com>

Closes #3644 from liancheng/parquet-tests and squashes the following commits:

800e745 [Cheng Lian] Enforces ordering of test output
3bb8731 [Cheng Lian] Refactors HiveParquetSuite
aa2cb2e [Cheng Lian] Decouples ParquetTest and TestSQLContext
7b43a68 [Cheng Lian] Updates ParquetTest Scaladoc
7f07af0 [Cheng Lian] Adds a new set of Parquet test suites
[SPARK-4744] [SQL] Short circuit evaluation for AND & OR in CodeGen

Author: Cheng Hao <hao.cheng@intel.com>

Closes #3606 from chenghao-intel/codegen_short_circuit and squashes the following commits:

f466303 [Cheng Hao] short circuit for AND & OR
[SPARK-4720][SQL] Remainder should also return null if the divider is 0.

This is a follow-up of SPARK-4593 (#3443).

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #3581 from ueshin/issues/SPARK-4720 and squashes the following commits:

c3959d4 [Takuya UESHIN] Make Remainder return null if the divider is 0.
[SPARK-4375] [SQL] Add 0 argument support for udf

Author: Cheng Hao <hao.cheng@intel.com>

Closes #3595 from chenghao-intel/udf0 and squashes the following commits:

a858973 [Cheng Hao] Add 0 arguments support for udf
[SPARK-4866] support StructType as key in MapType

This PR brings support of using StructType(and other hashable types) as key in MapType.

Author: Davies Liu <davies@databricks.com>

Closes #3714 from davies/fix_struct_in_map and squashes the following commits:

68585d7 [Davies Liu] fix primitive types in MapType
9601534 [Davies Liu] support StructType as key in MapType
[SPARK-4618][SQL] Make foreign DDL commands options case-insensitive

Using lowercase for ```options``` key to make it case-insensitive, then we should use lower case to get value from parameters.
So flowing cmd work
```
      create temporary table normal_parquet
      USING org.apache.spark.sql.parquet
      OPTIONS (
        PATH '/xxx/data'
      )
```

Author: scwf <wangfei1@huawei.com>
Author: wangfei <wangfei1@huawei.com>

Closes #3470 from scwf/ddl-ulcase and squashes the following commits:

ae78509 [scwf] address comments
8f4f585 [wangfei] address comments
3c132ef [scwf] minor fix
a0fc20b [scwf] Merge branch 'master' of https://github.com/apache/spark into ddl-ulcase
4f86401 [scwf] adding CaseInsensitiveMap
e244e8d [wangfei] using lower case in json
e0cb017 [wangfei] make options in-casesensitive
[Release] Update contributors list format and sort it

Additionally, we now warn the user when a duplicate author name
arises, in which case he/she needs to resolve it manually.
[HOTFIX] Fix RAT exclusion for known_translations file

Author: Josh Rosen <joshrosen@databricks.com>

Closes #3719 from JoshRosen/rat-fix and squashes the following commits:

1542886 [Josh Rosen] [HOTFIX] Fix RAT exclusion for known_translations file
[SPARK-4595][Core] Fix MetricsServlet not work issue

`MetricsServlet` handler should be added to the web UI after initialized by `MetricsSystem`, otherwise servlet handler cannot be attached.

Author: Saisai Shao <saisai.shao@intel.com>
Author: Josh Rosen <joshrosen@databricks.com>
Author: jerryshao <saisai.shao@intel.com>

Closes #3444 from jerryshao/SPARK-4595 and squashes the following commits:

434d17e [Saisai Shao] Merge pull request #10 from JoshRosen/metrics-system-cleanup
87a2292 [Josh Rosen] Guard against misuse of MetricsSystem methods.
f779fe0 [jerryshao] Fix MetricsServlet not work issue
[SPARK-4625] [SQL] Add sort by for DSL & SimpleSqlParser

Add `sort by` support for both DSL & SqlParser.

This PR is relevant with #3386, either one merged, will cause the other rebased.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #3481 from chenghao-intel/sortby and squashes the following commits:

041004f [Cheng Hao] Add sort by for DSL & SimpleSqlParser
[SPARK-4694]Fix HiveThriftServer2  cann't stop In Yarn HA mode.

HiveThriftServer2 can not exit automactic when changing the standy resource manager in Yarn HA mode.
The scheduler backend was aware of the AM had been exited so it call sc.stop to exit the driver process but there was a user thread(HiveThriftServer2 ) which was still alive and cause this problem.
To fix it, make a demo thread to detect the sparkContext is null or not.If the sc is stopped, call the ThriftServer.stop to stop the user thread.

Author: carlmartin <carlmartinmax@gmail.com>

Closes #3576 from SaintBacchus/ThriftServer2ExitBug and squashes the following commits:

2890b4a [carlmartin] Use SparkListener instead of the demo thread to stop the hive server.
c15da0e [carlmartin] HiveThriftServer2 can not exit automactic when changing the standy resource manager in Yarn HA mode
[SPARK-3698][SQL] Fix case insensitive resolution of GetField.

Based on #2543.

Author: Michael Armbrust <michael@databricks.com>

Closes #3724 from marmbrus/resolveGetField and squashes the following commits:

0a47aae [Michael Armbrust] Fix case insensitive resolution of GetField.
[SPARK-4493][SQL] Don't pushdown Eq, NotEq, Lt, LtEq, Gt and GtEq predicates with nulls for Parquet

Predicates like `a = NULL` and `a < NULL` can't be pushed down since Parquet `Lt`, `LtEq`, `Gt`, `GtEq` doesn't accept null value. Note that `Eq` and `NotEq` can only be used with `null` to represent predicates like `a IS NULL` and `a IS NOT NULL`.

However, normally this issue doesn't cause NPE because any value compared to `NULL` results `NULL`, and Spark SQL automatically optimizes out `NULL` predicate in the `SimplifyFilters` rule. Only testing code that intentionally disables the optimizer may trigger this issue. (That's why this issue is not marked as blocker and I do **NOT** think we need to backport this to branch-1.1

This PR restricts `Lt`, `LtEq`, `Gt` and `GtEq` to non-null values only, and only uses `Eq` with null value to pushdown `IsNull` and `IsNotNull`. Also, added support for Parquet `NotEq` filter for completeness and (tiny) performance gain, it's also used to pushdown `IsNotNull`.

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Author: Cheng Lian <lian@databricks.com>

Closes #3367 from liancheng/filters-with-null and squashes the following commits:

cc41281 [Cheng Lian] Fixes several styling issues
de7de28 [Cheng Lian] Adds stricter rules for Parquet filters with null
[SPARK-4755] [SQL] sqrt(negative value) should return null

Author: Daoyuan Wang <daoyuan.wang@intel.com>

Closes #3616 from adrian-wang/sqrt and squashes the following commits:

d877439 [Daoyuan Wang] fix NULLTYPE
3effa2c [Daoyuan Wang] sqrt(negative value) should return null
[SPARK-3739] [SQL] Update the split num base on block size for table scanning

In local mode, Hadoop/Hive will ignore the "mapred.map.tasks", hence for small table file, it's always a single input split, however, SparkSQL doesn't honor that in table scanning, and we will get different result when do the Hive Compatibility test. This PR will fix that.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #2589 from chenghao-intel/source_split and squashes the following commits:

dff38e7 [Cheng Hao] Remove the extra blank line
160a2b6 [Cheng Hao] fix the compiling bug
04d67f7 [Cheng Hao] Keep 1 split for small file in table scanning
[SPARK-4821] [mllib] [python] [docs] Fix for pyspark.mllib.rand doc

+ small doc edit
+ include edit to make IntelliJ happy

CC: davies  mengxr

Note to davies  -- this does not fix the "WARNING: Literal block expected; none found." warnings since that seems to involve spacing which IntelliJ does not like.  (Those warnings occur when generating the Python docs.)

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #3669 from jkbradley/python-warnings and squashes the following commits:

4587868 [Joseph K. Bradley] fixed warning
8cb073c [Joseph K. Bradley] Updated based on davies recommendation
c51eca4 [Joseph K. Bradley] Updated rst file for pyspark.mllib.rand doc.  Small doc edit.  Small include edit to make IntelliJ happy.
[HOTFIX][SQL] Fix parquet filter suite

Author: Michael Armbrust <michael@databricks.com>

Closes #3727 from marmbrus/parquetNotEq and squashes the following commits:

2157bfc [Michael Armbrust] Fix parquet filter suite
[SPARK-4856] [SQL] NullType instead of StringType when sampling against empty string or nul...

```
TestSQLContext.sparkContext.parallelize(
  """{"ip":"27.31.100.29","headers":{"Host":"1.abc.com","Charset":"UTF-8"}}""" ::
  """{"ip":"27.31.100.29","headers":{}}""" ::
  """{"ip":"27.31.100.29","headers":""}""" :: Nil)
```
As empty string (the "headers") will be considered as String in the beginning (in line 2 and 3), it ignores the real nested data type (struct type "headers" in line 1), and also take the line 1 (the "headers") as String Type, which is not our expected.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #3708 from chenghao-intel/json and squashes the following commits:

e7a72e9 [Cheng Hao] add more concise unit test
853de51 [Cheng Hao] NullType instead of StringType when sampling against empty string or null value