Bookmark Rewrite / Refactoring for App Framework

Hello there,

the reason for this rewrite was the request of a friend who wanted to access his bookmarks remotely in json formatting to use them in his WordPress Plugin (https://github.com/mario-nolte/oc2wp-bookmarks).

While working on this i decided to refactor everything to make use of the app framework because of its routing features. The app now features a restful api but still includes some legacy routes, so that for example the android bookmark app still works.

Check out the full code: https://github.com/ganomi/bookmarks

Features:
Dependency Injection for user and db is used througout the controllers
The Routing features a consistent rest api
The Routing provides some legacy routes, so that for exampe the Android Bookmarks App still works.
There is a publicly available api that provides access to bookmarks per user.
(This is usefull in connection with the WP Plugin https://github.com/mario-nolte/oc2wp-bookmarks)

This pull request now also features all the changes from Pull Request https://github.com/owncloud/bookmarks/pull/68 as well and all fixes to keep the original style and usability.
Should those functions return the data objects or the built sql string?