[SPARK-4003] [SQL] add 3 types for java SQL context

In JavaSqlContext, we need to let java program use big decimal, timestamp, date types.

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

Closes #2850 from adrian-wang/javacontext and squashes the following commits:

4c4292c [Daoyuan Wang] change underlying type of JavaSchemaRDD as scala
bb0508f [Daoyuan Wang] add test cases
3c58b0d [Daoyuan Wang] add 3 types for java SQL context