Plexbmc sections

Hi,

Two small changes:
1. added a "nocat" option to the skin runscript.  This tells plexbmc to only display a single "shared..." entry for all section types.  Previously is created one per type (movies, tv,music,pictures) - which meant 4 "shared..." entries on the home page.  You only get this with myplex setup and the "shared" link option turned on.
2. Added a refresh entry to settings - so that cached data can be flushed and recreated.