Scopes for Tag Frequency

Ben, I created this branch for the tag scopes we discussed. Now, if we
need to break this down further for things like used_at_least_once for
questions, users, etc. I can create more scopes to that effect as well.
Tag management tweaks

- don't display unused tags in the tag autocomplete field
- master list of all tags and frequency
- link to master list added to bottom of "Everything tagged with" pages
crudely highlight unanswered questions from states

- first stab
fix display of response images
Sort by resolved at, and indicated time resolved on question list
don't show reassignment time if resolved
better designed expert profile

larger description, tags grouped with bio, name and avatar moved to one
line
Merge branch 'development' into user_meta