Make the uses widget nicer.

Main changes include:

• Fix contexts not being clickable (they were clickable but didn't work)
• Remove the blue arrows; all widgets are expanded by default and can be collapsed with a small link in the text instead. This operation is not common enough to justify such a huge ugly button. (The main problem with the button was that it looked ugly, tough)
• Contexts without actual uses are always sorted last.
• Add some nice icons to the list.
• Remove all the ugly frames.
• Make text displaying code use a fixed-width font.
• Make the tooltip use a fixed-width font too, make it smaller (just 2 lines of context instead of 3), and highlight the line with the use by making it bold-face.
• Re-format and rename all the widget headers to be more readable and look nicer.

REVIEW:107296