Expanded background chooser to include options for single slides and all
slides
Updated chooser to set background on a per-slide or per-deck basis
Removed the context menu
Added the ability to reset the background to the deck default
Added the transparency checkerboard pattern
Fixed various bugs with background color application and preview
Adding styles for per-slide bg/surface images
Notes on how to go about rendering the per-slide surfaces
Picks the surface bg when previewing a reset of the slide bg for all
slides
Wired to observe background color changes for an individual slide
Correctly apply the backgrounds to handouts
Updated the shape selector to conform to the new dropdown interface
Image selection for bg
Merge remote-tracking branch 'origin/master' into per-slide-bgs-and-surfaces

Conflicts:
	app/styles/transition_editor/slideTable.css
Added the ability to insert images for slide backgrounds
Made the background preview smarter about removing classes
Enabled preview of surface selection on the slide editor.
Renders background images to presentations
Temporary remove of strut-surface::after stuff as it interfered with
component selection
Updated impress