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
add test
Merge branch 'master' into performanceDisplay

Conflicts:
	CHANGES.md
spelling
create textnodes
Merge pull request #1425 from AnalyticalGraphicsInc/performanceDisplay

Performance display