[SPARK-4713] [SQL] SchemaRDD.unpersist() should not raise exception if it is not persisted

Unpersist a uncached RDD, will not raise exception, for example:
```
val data = Array(1, 2, 3, 4, 5)
val distData = sc.parallelize(data)
distData.unpersist(true)
```

But the `SchemaRDD` will raise exception if the `SchemaRDD` is not cached. Since `SchemaRDD` is the subclasses of the `RDD`, we should follow the same behavior.

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

Closes #3572 from chenghao-intel/try_uncache and squashes the following commits:

50a7a89 [Cheng Hao] SchemaRDD.unpersist() should not raise exception if it is not persisted
[SPARK-4662] [SQL] Whitelist more unittest

Whitelist more hive unit test:

"create_like_tbl_props"
"udf5"
"udf_java_method"
"decimal_1"
"udf_pmod"
"udf_to_double"
"udf_to_float"
"udf7" (this will fail in Hive 0.12)

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

Closes #3522 from chenghao-intel/unittest and squashes the following commits:

f54e4c7 [Cheng Hao] work around to clean up the hive.table.parameters.default in reset
16fee22 [Cheng Hao] Whitelist more unittest
[SPARK-4639] [SQL] Pass maxIterations in as a parameter in Analyzer

fix a TODO in Analyzer:
// TODO: pass this in as a parameter
val fixedPoint = FixedPoint(100)

Author: Jacky Li <jacky.likun@huawei.com>

Closes #3499 from jackylk/config and squashes the following commits:

4c1252c [Jacky Li] fix scalastyle
820f460 [Jacky Li] pass maxIterations in as a parameter
[SPARK-4293][SQL] Make Cast be able to handle complex types.

Inserting data of type including `ArrayType.containsNull == false` or `MapType.valueContainsNull == false` or `StructType.fields.exists(_.nullable == false)` into Hive table will fail because `Cast` inserted by `HiveMetastoreCatalog.PreInsertionCasts` rule of `Analyzer` can't handle these types correctly.

Complex type cast rule proposal:

- Cast for non-complex types should be able to cast the same as before.
- Cast for `ArrayType` can evaluate if
  - Element type can cast
  - Nullability rule doesn't break
- Cast for `MapType` can evaluate if
  - Key type can cast
  - Nullability for casted key type is `false`
  - Value type can cast
  - Nullability rule for value type doesn't break
- Cast for `StructType` can evaluate if
  - The field size is the same
  - Each field can cast
  - Nullability rule for each field doesn't break
- The nested structure should be the same.

Nullability rule:

- If the casted type is `nullable == true`, the target nullability should be `true`

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

Closes #3150 from ueshin/issues/SPARK-4293 and squashes the following commits:

e935939 [Takuya UESHIN] Merge branch 'master' into issues/SPARK-4293
ba14003 [Takuya UESHIN] Merge branch 'master' into issues/SPARK-4293
8999868 [Takuya UESHIN] Fix a test title.
f677c30 [Takuya UESHIN] Merge branch 'master' into issues/SPARK-4293
287f410 [Takuya UESHIN] Add tests to insert data of types ArrayType / MapType / StructType with nullability is false into Hive table.
4f71bb8 [Takuya UESHIN] Make Cast be able to handle complex types.
[SQL] Remove unnecessary case in HiveContext.toHiveString

a follow up of #3547
/cc marmbrus

Author: scwf <wangfei1@huawei.com>

Closes #3563 from scwf/rnc and squashes the following commits:

9395661 [scwf] remove unnecessary condition
[SPARK-4828] [SQL] sum and avg on empty table should always return null

So the optimizations are not valid. Also I think the optimization here is rarely encounter, so removing them will not have influence on performance.

Can we merge #3445 before I add a comparison test case from this?

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

Closes #3675 from adrian-wang/sumempty and squashes the following commits:

42df763 [Daoyuan Wang] sum and avg on empty table should always return null
[SQL] enable empty aggr test case

This is fixed by SPARK-4318 #3184

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

Closes #3445 from adrian-wang/emptyaggr and squashes the following commits:

982575e [Daoyuan Wang] enable empty aggr test case
[SPARK-4825] [SQL] CTAS fails to resolve when created using saveAsTable

Fix bug when query like:
```
  test("save join to table") {
    val testData = sparkContext.parallelize(1 to 10).map(i => TestData(i, i.toString))
    sql("CREATE TABLE test1 (key INT, value STRING)")
    testData.insertInto("test1")
    sql("CREATE TABLE test2 (key INT, value STRING)")
    testData.insertInto("test2")
    testData.insertInto("test2")
    sql("SELECT COUNT(a.value) FROM test1 a JOIN test2 b ON a.key = b.key").saveAsTable("test")
    checkAnswer(
      table("test"),
      sql("SELECT COUNT(a.value) FROM test1 a JOIN test2 b ON a.key = b.key").collect().toSeq)
  }
```

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

Closes #3673 from chenghao-intel/spark_4825 and squashes the following commits:

e8cbd56 [Cheng Hao] alternate the pattern matching order for logical plan:CTAS
e004895 [Cheng Hao] fix bug
[SPARK-4742][SQL] The name of Parquet File generated by AppendingParquetOutputFormat should be zero padded

When I use Parquet File as a output file using ParquetOutputFormat#getDefaultWorkFile, the file name is not zero padded while RDD#saveAsText does zero padding.

Author: Sasaki Toru <sasakitoa@nttdata.co.jp>

Closes #3602 from sasakitoa/parquet-zeroPadding and squashes the following commits:

6b0e58f [Sasaki Toru] Merge branch 'master' of git://github.com/apache/spark into parquet-zeroPadding
20dc79d [Sasaki Toru] Fixed the name of Parquet File generated by AppendingParquetOutputFormat
[SPARK-4829] [SQL] add rule to fold count(expr) if expr is not null

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

Closes #3676 from adrian-wang/countexpr and squashes the following commits:

dc5765b [Daoyuan Wang] add rule to fold count(expr) if expr is not null
MAINTENANCE: Automated closing of pull requests.

This commit exists to close the following pull requests on Github:

Closes #3488 (close requested by 'pwendell')
Closes #2939 (close requested by 'marmbrus')
Closes #3173 (close requested by 'marmbrus')