DDL for FOREIGN KEY.
CREATE TABLE to AIS (via Protobuf).
ALTER TABLE cases.
I_S tables, \d support.
YAML tests for DDL.
RESTRICT cases of DML processing.
Error handling directly by the store.
YAML tests for RESTRICT cases.
Use operators to handle actions other than RESTRICT / NO ACTION.
Add some tests for ON DELETE SET DEFAULT and ON UPDATE CASCADE.
Need two Update handler methods to do CASCADE.
Refactor error checking and reporting to be more easily handled by other stores.
merge MMcM: Foreign key support

Merge pull request #1092 from MMcM/sql-layer/foreign-keys
https://github.com/FoundationDB/sql-layer/pull/1092