[SPARK-4272] [SQL] Add more unwrapper functions for primitive type in TableReader

Currently, the data "unwrap" only support couple of primitive types, not all, it will not cause exception, but may get some performance in table scanning for the type like binary, date, timestamp, decimal etc.

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

Closes #3136 from chenghao-intel/table_reader and squashes the following commits:

fffb729 [Cheng Hao] fix bug for retrieving the timestamp object
e9c97a4 [Cheng Hao] Add more unwrapper functions for primitive type in TableReader