Change from DeveloperError to RuntimeError for actual GeoJSON processing.
Cleanup promise usage.
Tweak to DynamicObject.merge.
Standardize casing.

1. GeoJSON is the format name.
2. geojson is the extension we use.
3. geoJson is the identifier casing.
More changes after review.
Merge pull request #890 from AnalyticalGraphicsInc/geojson

GeoJSON support
Merge branch 'master' into dynamicScene-cleanup