itemsList: Allow more room for buttons, resulting in a better balance with
the scrollbar.  Also allows one more button on screens without the
headingList.

Adjust the background alpha on the OSD.
headingList: square-up the selected item, and allow it to be narrower.
Give the headingList, groupsList and itemsList a minor 'face lift'.  Make
the lines a little thinner to give them a more elegant look.  Use ellipses
for the 'highlights'.  Use a scrollbar instead of arrows for the itemsList.