Reorganize CesiumViewer module configuration.

Flip the baseUrl around so that CesiumViewer is more like a self-contained application which pulls in Cesium modules using path configuration with a Cesium prefix.

Also fix build script to include the Cesium copyright header at the top of the built file.
Upgrade topojson from 1.6.8 to 1.6.18.
Merge pull request #2199 from AnalyticalGraphicsInc/cesiumViewerPathCleanup

Reorganize CesiumViewer module configuration.
Merge pull request #2202 from AnalyticalGraphicsInc/topojson-1.6.18

Upgrade topojson from 1.6.8 to 1.6.18.
Merge branch 'master' into tilt

Conflicts:
	CHANGES.md