Misc fixes for file patrol

Misc fixes for file patrol

This makes the following (minor) fixes to file patrol:
- If a documentation page for a file was recently created
before the file itself was uploaded, and the page creation
was patrolled, this now allows to patrol the file upload
from the file documentation footer.
- It attempts to retrieve a recent change for the latest
file upload, even if patrolled, so that this info can
be cached.
- It makes some extra code comments.

Change-Id: Ibdebcbbee7c081b99372c44ca64b5ddd86ae5ace