Notifications for new posts, API changes, several other things ...

First of all sorry for this mixture of changes, I made a mistake while using git :)

The changes are:
- API: The API was compared against the twitter and statusnet documentation and several things were made to make it more compatible
- The network value is now available in the thread template
- Notifications for new posts: When this option is activated for a contact, then you get a notification for every new post
- In "vier" the design was changed slightly, so that every network has a different background color
- OStatus complete conversation: This change should reduce the load of statusnet servers so that they only get pulled once in a while.