Refactor the hardcoded event actions (notifiables) to use a class

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4220 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine.rb

@@ -8,6 +8,7 @@ require 'redmine/core_ext'
 require 'redmine/themes'
 require 'redmine/hook'
 require 'redmine/plugin'
+require 'redmine/notifiable'
 require 'redmine/wiki_formatting'
 require 'redmine/scm/base'