clearify avatar_id arg for link_to_name

Also enable displaying the fallback avatar by setting it to 0.
always display the owner in page lists, cleanup

This will make caching a lot easier. Also reduces complexity.

Plus i don't think it's a good idea to leave out the owner - and thus often the group context. Page titles are sometimes meaningless without.
cache page rows based on updated_at

expire them when owner or updated_by avatars change
Merge pull request #79 from Crabgrass/feature/4354-cache-page-rows

Feature/4354 cache page rows