convert PerformanceDisplay from canvas to div
update cesium viewer for changes
Merge branch 'master' into performanceDisplay
update style
update cesium viewer
update doc
Merge branch 'master' into performanceDisplay

Conflicts:
	CHANGES.md
update api
changes.md
Tweak CHANGES.md
add test
Merge branch 'master' into performanceDisplay

Conflicts:
	CHANGES.md
Merge branch 'performanceDisplay' into inspector

Conflicts:
	Source/Scene/PerformanceDisplay.js
update for new performance display