Reject queries requiring halloween transformation if table is FK referenced
Reject DELETE and UPDATE of fk referenced if query contains referencing
merge nathanlws: Reject Halloween vulnerable queries on FK referenced tables

Merge pull request #1281 from nathanlws/sql-layer/reject-fk-halloween
https://github.com/FoundationDB/sql-layer/pull/1281
Optimize groupKeyIterator() to use get() instead of getRange().