Aktuelles Notifications

- added automatic notifications for "Aktuelles"
- fixed canteen parsers
- other minor fixes
- tested on Android 4.2. No known issues.

Notification preview:
![fb4-aktuelles-notification](https://f.cloud.github.com/assets/5065947/1851049/6ba5dc3e-76e1-11e3-974f-48791c10d788.png)