R1:c1331bcb7ba6

Cache user notification and message counts

Summary:
Ref T4103. Ref T10078. This puts a user cache in front of notification and message counts.

This reduces the number of queries issued on every page by 4 (2x building the menu, 2x building Quicksand data).

Also fixes some minor issues:

- Daemons could choke on sending mail in the user's translation.
- No-op object updates could fail in the daemons.
- Questionable data access pattern in the file query coming out of the profile file cache.

Test…