Implement the IsDeferrable and InitiallyDeferred settings in the
Information_Schema.table_constraints table, plus test to show it works
as designed.
merge tjoneslo: Implement the IsDeferrable and InitiallyDeferred settings in the

Merge pull request #1355 from tjoneslo/sql-layer/implement-is-deferrable-for-table-constraints
https://github.com/FoundationDB/sql-layer/pull/1355