[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.