[WIP] Added tags/favorites support

:construction: WIP


Doesn't work.
If I use:
```
return $c->query('TagManager')->load('files');
```
I get
```
Message: Identifier "TagManager" is not defined.
File: /srv/www/htdocs/owncloud/3rdparty/pimple/pimple/src/Pimple/Container.php
```