Renamed prototypes, added (blank) left panel

Kind of a large commit, but I just kept going after I renamed the files
and it was all over from there, so here it is...

 - Renamed canvas_draw -> Brush, draw_manager -> BrushManager,
   server_comm -> ServerComms.js, local_draw.js -> LocalBrush.js
 - Added NullComms so we can test local only
 - Added a blank left panel, and fixed some offset issues in LocalBrush
   to compensate

Still having some issues (why is the scrollbar showing?)