[SPARK-2339][SQL] SQL parser in sql-core is case sensitive, but a table alias is converted to lower case when we create Subquery

Reported by http://apache-spark-user-list.1001560.n3.nabble.com/Spark-SQL-Join-throws-exception-td8599.html
After we get the table from the catalog, because the table has an alias, we will temporarily insert a Subquery. Then, we convert the table alias to lower case no matter if the parser is case sensitive or not.
To see the issue ...
```
val sqlContext = new org.apache.spark.sql.SQLContext(sc)
import sqlContext.createSchemaRDD

case class Person(name: String, age: Int)

val people = sc.textFile("examples/src/main/resources/people.txt").map(_.split(",")).map(p => Person(p(0), p(1).trim.toInt))
people.registerAsTable("people")

sqlContext.sql("select PEOPLE.name from people PEOPLE")
```
The plan is ...
```
== Query Plan ==
Project ['PEOPLE.name]
 ExistingRdd [name#0,age#1], MapPartitionsRDD[4] at mapPartitions at basicOperators.scala:176
```
You can find that `PEOPLE.name` is not resolved.

This PR introduces three changes.
1.  If a table has an alias, the catalog will not lowercase the alias. If a lowercase alias is needed, the analyzer will do the work.
2.  A catalog has a new val caseSensitive that indicates if this catalog is case sensitive or not. For example, a SimpleCatalog is case sensitive, but
3.  Corresponding unit tests.
With this PR, case sensitivity of database names and table names is handled by the catalog. Case sensitivity of other identifiers are handled by the analyzer.

JIRA: https://issues.apache.org/jira/browse/SPARK-2339

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1317 from yhuai/SPARK-2339 and squashes the following commits:

12d8006 [Yin Huai] Handling case sensitivity correctly. This patch introduces three changes. 1. If a table has an alias, the catalog will not lowercase the alias. If a lowercase alias is needed, the analyzer will do the work. 2. A catalog has a new val caseSensitive that indicates if this catalog is case sensitive or not. For example, a SimpleCatalog is case sensitive, but 3. Corresponding unit tests. With this patch, case sensitivity of database names and table names is handled by the catalog. Case sensitivity of other identifiers is handled by the analyzer.

(cherry picked from commit c0b4cf097de50eb2c4b0f0e67da53ee92efc1f77)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2386] [SQL] RowWriteSupport should use the exact types to cast.

When execute `saveAsParquetFile` with non-primitive type, `RowWriteSupport` uses wrong type `Int` for `ByteType` and `ShortType`.

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

Closes #1315 from ueshin/issues/SPARK-2386 and squashes the following commits:

20d89ec [Takuya UESHIN] Use None instead of null.
bd88741 [Takuya UESHIN] Add a test.
323d1d2 [Takuya UESHIN] Modify RowWriteSupport to use the exact types to cast.

(cherry picked from commit 4deeed17c4847f212a4fa1a8685cfe8a12179263)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2375][SQL] JSON schema inference may not resolve type conflicts correctly for a field inside an array of structs

For example, for
```
{"array": [{"field":214748364700}, {"field":1}]}
```
the type of field is resolved as IntType. While, for
```
{"array": [{"field":1}, {"field":214748364700}]}
```
the type of field is resolved as LongType.

JIRA: https://issues.apache.org/jira/browse/SPARK-2375

Author: Yin Huai <huaiyin.thu@gmail.com>

Closes #1308 from yhuai/SPARK-2375 and squashes the following commits:

3e2e312 [Yin Huai] Update unit test.
1b2ff9f [Yin Huai] Merge remote-tracking branch 'upstream/master' into SPARK-2375
10794eb [Yin Huai] Correctly resolve the type of a field inside an array of structs.

(cherry picked from commit f0496ee10847db921a028a34f70385f9b740b3f3)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2376][SQL] Selecting list values inside nested JSON objects raises java.lang.IllegalArgumentException

JIRA: https://issues.apache.org/jira/browse/SPARK-2376

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1320 from yhuai/SPARK-2376 and squashes the following commits:

0107417 [Yin Huai] Merge remote-tracking branch 'upstream/master' into SPARK-2376
480803d [Yin Huai] Correctly handling JSON arrays in PySpark.

(cherry picked from commit 4352a2fdaa64efee7158eabef65703460ff284ec)
Signed-off-by: Michael Armbrust <michael@databricks.com>