Basic autocomplete for admin posts tags

Similar to the skins autocomplete: basic LIKE search, maximum MAX_RECENT items. Can be tweaked by further requests.
Rake task to destroy all unused admin post tags
Update .gitignore

added vim swp files
Merge branch 'master' of git://github.com/otwcode/otwarchive

updating my master branch
tag gl adjustment
tag gl css fix
standardized terms, measures
Update public/stylesheets/site/2.0/16-zone-system.css

spaces
Merge branch 'master' of git://github.com/otwcode/otwarchive
Merge branch 'master' of git://github.com/otwcode/otwarchive
Merge branch 'master' of git://github.com/otwcode/otwarchive
3806 add Twitter Javascript to chapters/show
3806 Move Twitter JavaScript to work navigation partial so it is included for chapters
Merge branch 'master' of git://github.com/otwcode/otwarchive
2394 Redirects user to chapter page if work is multichaptered
Link to chapters in Entire Work mode instead of Chapter by Chapter mode
3812 Admin post filter labels should select associated form elements
3812 Make Filters text on admin posts index translateable
get the types required for matching in a particular challenge
Major revision of potential matching for speed

This drastically reduces the time it takes to generate potential matches for a large challenge with many options by reducing the number of signups checked to only those that have any chance of a match (i.e., sharing at least one required tag). Finding these signups can be done with fast SQL-only queries.

Signed-off-by: Naomi Novik <shalott@gmail.com>