Merge filter and notification servers, have both tasks run on the same servers

Review: http://codereview.adblockplus.org/5302563972841472/

--HG--
rename : modules/filterserver/files/easylist-downloads.adblockplus.org => modules/filterserver/templates/easylist-downloads.adblockplus.org.erb
rename : modules/notificationserver/files/notification.adblockplus.org => modules/notificationserver/templates/notification.adblockplus.org.erb