Story 1030: Clean up ui.less

In the process:
* remove old watchstar code
* remove lots of unused, undocumented CSS rules
* convert multiple rules (e.g. background-*) into a single rule
  (background)
* increase the size of clearing X in the search input

Change-Id: I4929cc38eb7154f2b010ef6378969a6175289947
Merge "Story 1030: Clean up ui.less"