[SPARK-4861][SQL] Refactory command in spark sql

Remove ```Command``` and use ```RunnableCommand``` instead.

Author: wangfei <wangfei1@huawei.com>
Author: scwf <wangfei1@huawei.com>

Closes #3712 from scwf/cmd and squashes the following commits:

51a82f2 [wangfei] fix test failure
0e03be8 [wangfei] address comments
4033bed [scwf] remove CreateTableAsSelect in hivestrategy
5d20010 [wangfei] address comments
125f542 [scwf] factory command in spark sql