Stopped usage of Index.isForeignKey()
Updated meta data versions, and protobuf related files
removal of index.constraint field
Removal of DDLGenerator
minor clean-up
Update on comments, removed Schema parameter from Index.isConnectedToFK(), removed one unused case handling Primary Indexes
merge SytzeH: Removal of index.constraint field, and DDLGenerator()

Merge pull request #1360 from SytzeH/sql-layer/indexCon
https://github.com/FoundationDB/sql-layer/pull/1360