branches/impl-build_system (refs #613):
- Add event system (tasks: TargetListener, TaskListener, MessageListener)
- Add ability to create objects within build files (types: Object)
- Add ability to import one buildfile into another (tasks: Import)
- Restructure tasks directory (-> phing/, namespaced, and also includes types)
- Remove Initialize task and move its functionality to AgaviTask
- Update e-mail address
- Bugfixes