notifications 6.x-4.0-alpha3

New features, code and performance improvements:
- Added Custom Notifications and Content type extension modules
- New template testing feature (for node events) in Notifications Tools
- Extended notifications_* hooks, easier coding and performance improvements
- Reworked templates, configurable templates for events (support for templates per content type)
- Major OOP rework: Subscriptions, Events, etc
- Support for Anonymous destinations / subscriptions. New notifications_anonymous module
- Reorganized modules: notifications_digest, notifications_tools (Smaller notifications module)
- Implemented 7.x like API for static variables,
- API and storage improvements for upcoming multilingual support.