Rename FullscreenWidget to FullscreenButton and associated files

Also add specs for the widget, which cover as much as we can since we can't actually use Fullscreen mode in tests.
Fire cut at HomeButton widget

Also clean up some other widget code and remove unecessary public properties.
HomeButton and createCommand specs.
Update CHANGES.
Fix CSS
Fixes after review.
Merge branch 'master' into homeButton
Merge pull request #753 from AnalyticalGraphicsInc/homeButton

Widget cleanup and new HomeButton widget.