addded initial version of WallGeometry
added WallGeometry sandcastle demo
code clarifications for WallGeometry
Merge remote-tracking branch 'upstream/batching' into batching
added WallGeometry comment into CHANGES.md
added PolygonGeometry
updated WallGeometry to expect positions in Cartesian instead of
Cartographic
added BaseLayerPicker capability to receive an array of providers
and to accept ImageLayers as well as providers
added destroy function to Timeline
modifications re Patrick Cozzi's git pull reivew feedback
Merge branch 'batching' of https://github.com/AnalyticalGraphicsInc/cesium into batching
Merge pull request #778 from akosmaroy/batching

addded initial version of WallGeometry