improve usability of 'Photos' entry

The entry '**Photos**' displays a bucket of thumbnails sorted by upload-date (i guess).
There is no option to reveal any hierarchy or order them differently and it takes ages to display large amounts of thumbnails. This is not very usefull i think.

### solution i'd like
This menu-entry should probably behave more like the nc-gallery-app.
in particular:
- respect ```.nomedia```-files!
- view hierarchically as Album-folders to be able to drill down (that would also reduce the thumbnail-latency i suppose)
- **Bonus**:
- support ```gallery.cnf``` files
- pause/play button
- rename the whole thing to 'Gallery'