[SPARK-7805] [SQL] Move SQLTestUtils.scala and ParquetTest.scala to src/test

https://issues.apache.org/jira/browse/SPARK-7805

Because `sql/hive`'s tests depend on the test jar of `sql/core`, we do not need to store `SQLTestUtils` and `ParquetTest` in `src/main`. We should only add stuff that will be needed by `sql/console` or Python tests (for Python, we need it in `src/main`, right? davies).

Author: Yin Huai <yhuai@databricks.com>

Closes #6334 from yhuai/SPARK-7805 and squashes the following commits:

af6d0c9 [Yin Huai] mima
b86746a [Yin Huai] Move SQLTestUtils.scala and ParquetTest.scala to src/test.