[SPARK-15914][SQL] Add deprecated method back to SQLContext for backward source code compatibility

## What changes were proposed in this pull request?

Revert partial changes in SPARK-12600, and add some deprecated method back to SQLContext for backward source code compatibility.

## How was this patch tested?

Manual test.

Author: Sean Zhong <seanzhong@databricks.com>

Closes #13637 from clockfly/SPARK-15914.