notifications 5.x-1.0-beta1

Lots of improvements and bug fixes:
- Fixed Notifications cron processing records ignoring module name by Brian Neisler, http://drupal.org/node/244571
- Implemented notifications sender option, see http://drupal.org/node/227377
- Resolved naming conflict with other modules by Lynn, http://drupal.org/node/232610
- Rewritten notifications_load_user() to use messaging_load_user() so they share caching
- Subscriptions fields not mandatory anymore, http://drupal.org/node/237972
- Improved digesting format for new posts, http://drupal.org/node/218745
- Delete node/feed/group subscriptions when they don't apply anymore, http://drupal.org/node/236194
- Removed handling of pull messaging, moved that feature to messaging module [message queueing].