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
Merge branch 'refs/heads/master' into 0.9.12-issue-3177-admintags
Merge branch 'refs/heads/master' into 0.9.12-issue-3177-admintags
Merge branch 'refs/heads/master' into updated-issue-3177-admintags
Fix for Rspec SMTP errors
3308 change label for work skins on new work form
Change it on edit multiple, too
3308 Commit the CSS you tested, self -- .dashboard > form
Merge pull request #1555 from sarken/shutuptravis_userdashboardedition

Commenting out the oldest/newest series part of the user dashboard test
Merge pull request #1551 from elzj/rspec_error_fix

Fix for Rspec SMTP errors
Merge pull request #775 from CristinaRO/issue-3177-admintags

Issue 3177 admintags
Merge pull request #910 from sarken/issue_3308

3308 change label for work skins on new work form
Shut up the failing dashboard test again maybe