Search - add support for saving the UserId in the Index

- add the new "user_id" colum
- use -1 as a default value

This CL depends on that Framework CL for SearchIndexableData: 0d94539e67e997ed7687f33854fc581ce4668da5

See bug: #15837747 Search - update for Enterprise support

Change-Id: I0cf2866600732e8e99006050bf9ad388fa44b509