Enhanced apps management [WIP]

:construction: 

TODO:
* [x] merge Handlebars.js pull request which this depends on https://github.com/owncloud/core/pull/10413
* [ ] add »Recommended« tag to recommended apps (directly next to the score)
* [ ] add link to »More apps in the store …«
* [ ] sort by name (in the future by rating + downloads)
* [ ] make it faster!
There we go: https://github.com/owncloud/core/commit/8d82df351903311bc476152f8d58db25987771d6