Initial Refactoring for Settings / Applications Management

Hi, since ownCloud 6 has been released, this is my initial work for ownCloud 7 settings. I am sort of trying to take care of it in my free time. 
This is the first attempt of organising the application management code. Once this is accepted/included, I will start refactoring the other 2 (user management and personal settings) and the current JS which I have not changed yet (minus some change in classes and id names). The new JS lies dead in one of my old branches.
It also has some enhancements in the form of using app-navigation from the core in the app listing and of course little better styles. 

Please check: @karlitschek @icewind1991 @DeepDiver1975 @owncloud/designers @jancborchardt