Minor tweaks to layout of file selector/download buttons. Dialogs have max-width of 100% now (so the About dialog looks alright on narrow screens). Tapping on a link in the content when the mobile menu is prevented (tapping content should just close the menu).
Fix for invite dialog being behind the overlay.
Blue sub sub menu
Keep middle pane actions (groups/graders) vertically centred. Converted some old modals to use the newer ModalMarkus modals.
Made some links into buttons so they're easier to tap
file_selector margins
Merge conflicts
Merge pull request #1544 from arkon94/mobile-r2

Minor UI tweaks