Added "Shared with link" sidebar section in files app

Added section to only show link shares.

Please note that the filtering is currently done on the client side
which might not be the most efficient way of doing it.
Fix mime type returning for "shared with others" files

Use "path" instead of "file_target", as the latter is not always set /
reliable.
Fixed wording to "Shared by link"
hide navigation by default, not only on small screens, first step
adjust controls bar position for removed nav bar
toggle the navigation on desktop, not only on mobile
show appname next to logo for better hint at navigation
fix navigation bubble width and height on mobile
Remove obsoleted code to trigger navigation menu

Now that the navigation menu is always togglable, the media query
dependent code can be removed.
drop "push" element - no sticky footer needed anymore
reduce font size of appname in header
cut ownCloud text from logo when logged in, place appname there
show appname on mobile since now there's enough space
separate home icon and menu toggle
show loading feedback
show 'Apps' as fallback label for app switcher if no app title is present (for example in Settings)
better loading feedback for app start, move from JS to CSS
move 'add apps' entry into normal navigation instead of a new line
rearrange CSS, remove duplicate code
more CSS rearranging, removing duplicate code