Make sure we version all tables whose rows depend on the SCKAN release.

[dbrnz]

1. All relevant tables need a source column.
2. This column needs to be included in indexes.
3. It needs to be set to the knowledge source when adding/updating rows.
4. Querying needs to include source in joins, and or specific queries against flatmaps, it must be set to the flatmap's knowledge source.

A good time to implement this is when the schema and database content is updated as part of #37.