convert PerformanceDisplay from canvas to div
update cesium viewer for changes
Merge branch 'master' into performanceDisplay
update style
update cesium viewer
update doc
Add support for a minimum level on OpenStreetMapImageryProvider
Update CHANGES.md
Check the number of tiles at the minimum level
Merge pull request #1409 from andre-nunes/minLevel

OpenStreetMapImageryProvider can now make use of minimum level
Minor tweaks to OSM imagery provider.
Merge pull request #1422 from AnalyticalGraphicsInc/minorOsmTweaks

Minor tweaks to OSM imagery provider.
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
spelling
create textnodes