Replace GroupIndexCreator with direct DDL.
merge nathanlws: Replace GroupIndexCreator with direct DDL.

Merge pull request #1051 from nathanlws/sql-layer/remote-test-gi-creator
https://github.com/FoundationDB/sql-layer/pull/1051
Remove old types code and associated confused comment.
Add a new test for various conversions at the script boundary.
Add casting of output values, too.