* Adds watched_by class method in ActsAsWatchable
* Adds Issue#recently_updated, Issue#with_limit and Issue#on_active_project

  #2482

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3557 e93f8b46-1217-0410-a6f0-8f06a7374b81