Minor code change due to Optiq 0.6-SNAPSHOT change.

Rename ConnectionConfig to DrillConnectionConfig due to optiq-0.6-SNAPSHOT add an interface with same name.

Signed-off-by: vkorukanti <venki.korukanti@gmail.com>
More minor changes due to Optiq 0.6-SNAPSHOT:
1. org.eigenbase.rel.Direction capitlization changes
2. DrillAggregateRel and DrillProjectRel interface changes
3. SqlExplain interface changes
Copy of Optiq's Sql parser file
SHOW TABLES/DATABASES, DESCRIBE TABLE (wip)
1. Need to improve the testcases to verify the results
2. Extend DESCRIBE to handle schema.table.
More tests and missing file in prev commit
Cleanup and more tests also changed to parse identifier instead of string literal in few statements