Fix an error when using knockout.track without a list of properties.
Merge pull request #1545 from AnalyticalGraphicsInc/knockoutES5Fix

Fix an error when using knockout.track without a list of properties.
Add a loading indicator to the HTML sanitizer.
Merge pull request #1546 from AnalyticalGraphicsInc/info-loading

Add a loading indicator to the HTML sanitizer.
Initialize cached widget sizes to undefined.

If the canvas is never resized after creation of a Cesium widget, we would never render.  Rather than caching canvas size at creation time, this ensures that we always run through the resize code at least once.
Use 0 instead of undefined for initial widget size.

Viewer needs lastWidth to always have a valid value and using 0.
Merge pull request #1547 from AnalyticalGraphicsInc/fix-resize

Initialize cached widget sizes to undefined.
Fix #1554 where a transparent point leaked its outline color.
Merge pull request #1555 from AnalyticalGraphicsInc/issue1554

Fix #1554 where a transparent point leaked its outline color.
Merge remote-tracking branch 'origin/master' into gltfDefaults
Default improvements