Reuse the map_bug_comment table as a more general history table of map_bugs including close and reopen events

This helps the rss feed to work on a per event basis rather than on a per bug basis

app/models/map_bug_comment.rb

@@ -5,6 +5,8 @@ class MapBugComment < ActiveRecord::Base
   belongs_to :map_bug, :foreign_key => 'bug_id'
   belongs_to :user, :foreign_key => 'commenter_id'
 
+   validates_inclusion_of :event, :in => [ "opened", "closed", "reopened", "commented", "hidden" ]
+
   validates_presence_of :id, :on => :update
   validates_uniqueness_of :id
   validates_presence_of :visible