Added US States GeoJSON to Viewer Gallery.

The new data is already covered by this section of LICENSE.md:

### Public domain data from Natural Earth

Free vector and raster map data @ naturalearthdata.com

Terms of use: http://www.naturalearthdata.com/about/terms-of-use/
Merge branch 'selection' into dataSourceBrowser-selection
Primitive descriptions for GeoJson, based on the balloon branch.
Imrpove GeoJSON name heuristic.
Fix comment.
Sanitize HTML loaded into the SelectionIndicator

This uses Google caja by default, specifically, a slightly tweaked
version of the JsHtmlSantizer object from https://github.com/mapbox/sanitize-caja.
Put the selection graphic behind other UI elements.
Allow the info box to stay open separately from the position.
Merge pull request #1411 from AnalyticalGraphicsInc/selection-sanitizeHtml

Sanitize HTML loaded into the SelectionIndicator
Rename descriptionText to descriptionHtml.
Merge remote-tracking branch 'origin/selection' into dataSourceBrowser-selection

Conflicts:
	Source/DynamicScene/GeoJsonDataSource.js