The Moodle UI should be functional in a viewport of 320px by 256px to
meet WCAG 1.4.10
this patch contains improvements to:
-prevent horizontal scrolling
-better wrapping of page header
-message drawer funtional on tiny screens
-remove indenting on courses
-prevent elements overlapping on quiz editing
-better navigation tabs
-fix colour picker
-quiz editing
Having a distinguishable class "activity-navigation" added to the activity
navigation allows that part to be easily styled. It could for example be
excluded from printing. Furthermore, this is providing consistency. Other
navigation elements have proper own classes as well.
