[SPARK-6672][SQL] convert row to catalyst in createDataFrame(RDD[Row], ...)

We assume that `RDD[Row]` contains Scala types. So we need to convert them into catalyst types in createDataFrame. liancheng

Author: Xiangrui Meng <meng@databricks.com>

Closes #5329 from mengxr/SPARK-6672 and squashes the following commits:

2d52644 [Xiangrui Meng] set needsConversion = false in jsonRDD
06896e4 [Xiangrui Meng] add createDataFrame without conversion
4a3767b [Xiangrui Meng] convert Row to catalyst