Awesomebar: add hover-scroll for long submenus

Really long submenus (such as the list of sections in courses with lots of sections) could not be reached in their entirety.  This patch makes the submenu scroll when the mouse is in the top or bottom 50px.
Awesomebar: Increase hover timer to 750ms

Increase the hover timer (which keeps the menus open when mousing out) from 500ms to 750ms to make menus linger just a little longer.