Fixed cleaning command for parallel grounding
Spouse example for psql/gp; draft of gp test architecture

- Added a test of psql spouse example
- Added test_gp.sh script
Fixing examples to let GP test work

- Mostly dealing with COPY / \\COPY issue. COPY has permission problems on GP.
- For Chunking, have not fixed the issue yet. Now on GP, chunking test will fail for both with/without parallel grounding.
Merge pull request #164 from HazyResearch/zifei-grounding-test

Added tests for Greenplum