Drop periodically_commit defaults
merge nathanlws: Drop periodically_commit defaults

Merge pull request #1297 from nathanlws/sql-layer/lower-periodically-commit
https://github.com/FoundationDB/sql-layer/pull/1297
merge nathanlws: Collapse DerivedTypesSchema into Schema

Merge pull request #1298 from nathanlws/sql-layer/collapse-qp-schemas
https://github.com/FoundationDB/sql-layer/pull/1298
Don't cause exception checking for retry
Expand test to general cover all DML
Save Schema used in all Statements and require set before use on context