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
3604 Update dropdown plugin
Make the jQuery setup a bit faster
Fix broken dl and div HTML and add translation strings on owned_tag_sets/show
Warnings, categories, and ratings should be comma separated on the tag set's show page
Bring it up to date with master so maybe I won't get an error on the associations page
Minify that JavaScript
Didn't mean to commit that other bootstrap dropdown file
Issue 3494: Moderators can delete PromptMeme sign-ups
Issue 3494: Now with tests
3842 Invalid HTML on challenge sign-ups page
Merge branch 'issue_3604' of https://github.com/sarken/otwarchive into Group17

# By sarken
# Via sarken
* 'issue_3604' of https://github.com/sarken/otwarchive:
  Didn't mean to commit that other bootstrap dropdown file
  Minify that JavaScript
  Make the jQuery setup a bit faster
  3604 Update dropdown plugin

Conflicts:
	app/views/layouts/_javascripts.html.erb
Merge branch 'issue_3730_3731' of https://github.com/sarken/otwarchive into Group17

# By sarken
# Via sarken
* 'issue_3730_3731' of https://github.com/sarken/otwarchive:
  Warnings, categories, and ratings should be comma separated on the tag set's show page
  Fix broken dl and div HTML and add translation strings on owned_tag_sets/show
Merge branch 'issue_3842' of https://github.com/sarken/otwarchive into Group17

# By sarken
# Via sarken
* 'issue_3842' of https://github.com/sarken/otwarchive:
  3842 Invalid HTML on challenge sign-ups page
Merge branch 'issue-3177-admintags' of github.com:CristinaRO/otwarchive into Group17

# By Cristina
# Via Cristina
* 'issue-3177-admintags' of github.com:CristinaRO/otwarchive:
  Rake task to destroy all unused admin post tags
  Basic autocomplete for admin posts tags
Merge branch 'issue_3494' of github.com:scottsds/otwarchive into Group17

# By Scott D. Sullivan
# Via Scott D. Sullivan
* 'issue_3494' of github.com:scottsds/otwarchive:
  Issue 3494: Now with tests
  Issue 3494: Moderators can delete PromptMeme sign-ups
Merge pull request #18 from otwstephanie/Group17

Group17