I've added functionality to create new StructType similar to how we add parameters to a new SparkContext.

I've also added tests for this type of creation.

Author: Ilya Ganelin <ilya.ganelin@capitalone.com>

Closes #6686 from ilganeli/SPARK-8056B and squashes the following commits:

27c1de1 [Ilya Ganelin] Rename
467d836 [Ilya Ganelin] Removed from_string in favor of _parse_Datatype_json_value
5fef5a4 [Ilya Ganelin] Updates for type parsing
4085489 [Ilya Ganelin] Style errors
3670cf5 [Ilya Ganelin] added string to DataType conversion
8109e00 [Ilya Ganelin] Fixed error in tests
41ab686 [Ilya Ganelin] Fixed style errors
e7ba7e0 [Ilya Ganelin] Moved some python tests to tests.py. Added cleaner handling of null data type and added test for correctness of input format
15868fa [Ilya Ganelin] Fixed python errors
b79b992 [Ilya Ganelin] Merge remote-tracking branch 'upstream/master' into SPARK-8056B
a3369fc [Ilya Ganelin] Fixing space errors
e240040 [Ilya Ganelin] Style
bab7823 [Ilya Ganelin] Constructor error
73d4677 [Ilya Ganelin] Style
4ed00d9 [Ilya Ganelin] Fixed default arg
67df57a [Ilya Ganelin] Removed Foo
04cbf0c [Ilya Ganelin] Added comments for single object
0484d7a [Ilya Ganelin] Restored second method
6aeb740 [Ilya Ganelin] Style
689e54d [Ilya Ganelin] Style
f497e9e [Ilya Ganelin] Got rid of old code
e3c7a88 [Ilya Ganelin] Fixed doctest failure
a62ccde [Ilya Ganelin] Style
966ac06 [Ilya Ganelin] style checks
dabb7e6 [Ilya Ganelin] Added Python tests
a3f4152 [Ilya Ganelin] added python bindings and better comments
e6e536c [Ilya Ganelin] Added extra space
7529a2e [Ilya Ganelin] Fixed formatting
d388f86 [Ilya Ganelin] Fixed small bug
c4e3bf5 [Ilya Ganelin] Reverted to using parse. Updated parse to support long
d7634b6 [Ilya Ganelin] Reverted to fromString to properly support types
22c39d5 [Ilya Ganelin] replaced FromString with DataTypeParser.parse. Replaced empty constructor initializing a null to have it instead create a new array to allow appends to it.
faca398 [Ilya Ganelin] [SPARK-8056] Replaced default argument usage. Updated usage and code for DataType.fromString
1acf76e [Ilya Ganelin] Scala style
e31c674 [Ilya Ganelin] Fixed bug in test
8dc0795 [Ilya Ganelin] Added tests for creation of StructType object with new methods
fdf7e9f [Ilya Ganelin] [SPARK-8056] Created add methods to facilitate building new StructType objects.