This allows for using following URLs:

* /package/$pkg_name/flag: Flag a package out-of-date
* /package/$pkg_name/unflag: Unflag a package
* /package/$pkg_name/notify: Enable comment notifications
* /package/$pkg_name/unnotify: Disable comment notifications
* /package/$pkg_name/vote: Vote for the package
* /package/$pkg_name/unvote: Remove vote

Note that this code is very hackish and should be refactored once we
drop support for legacy URLs.

Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>