Enable color variable selector for plots.
 - Users can now choose a color variable, but we don't do anything with it.
Merge branch 'fb_plots' into variableselector
Wire up color measure
 - We now request the data for the color measure, but we don't use it.
 - Fixed issue with variable selectors not remembering selection from
   active filter.
Enable color and shape scales on plot.
Render color variable selector in collapsed state.
Render color legend in collapsed state.
 - Show details on hover of glyph.
 - Added new style for a window with a triangle on the top.
Fix hover text for scatter plots.
 - Add subject id.
 - Add color measure.
 - Add proper formatting.
Merge branch 'variableselector' into fb_plots