Issue 31 database performance improvements
Initial raft of improvements in support of Issue 31, including:
- Performance-related database indexes.
- Suppression of obsolete calendar_free_busy_set property, unless explicitly configured on.
Also: 3. Fixes to windows create database script (Issue 32).
Note that this branch contains a database patch script, 1.2.12.sql, and a corresponding change to the version declared in the main install script. However since I am unsure of the release versioning strategy, this may need to be renamed or otherwise changed on merge.