[WIP] Bookmark application for newer versions of OC

:construction: Work in progress!

This will probably solve many issues regarding to design.

Eg: https://github.com/owncloud/bookmarks/issues/20

What needs to be done:

- [x] change leftcontent rightcontent into app-navigation & app-content
- [x] change bookmark_settings into app-settings
No, when is ok here :)