[WIP] Mobile optimization for base layout and Files app

:construction: Stuff left to do:

* [x] hide Rename and Versions. For that the file actions need classes like ```action-rename``` etc. @DeepDiver1975 need your help. :)
* [x] make the menu toggle for the navigation only work on mobile – it shouldn’t be possible to toggle the navigation on desktop. @PVince81 can you help here?
* [x] show better indicator that the logo includes a menu toggle. For example a little 3*3 grid icon
* [x] ideally use [Headroom.js](http://wicky.nillia.ms/headroom.js/) so the header and controls bar is hidden on scrolling down, but immediately shown on a bit of scrolling up. Important to preserve space on mobile – separate issue now: https://github.com/owncloud/core/issues/7826
* [x] retest on stock android browser Galaxy S3 @DeepDiver1975
* [x] landscape mode in non-mobile - style is ok - but actions are not shown – separate issue: https://github.com/owncloud/core/issues/7827
* [x] Upload process bar and cancel button deserve some love - they are rendered below the controls panel

And probably some more stuff I missed.

@karlitschek please check if the approach is fine in general.