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
Add aria-label to the unread message and notification icons.
Add aria-label to the total conversations, unread conversations
and unread messages in the overview.
Add aria-label to the pending contact requests in the overview
and also in the contacts tab.
Add aria-hidden to the last message date.
