Added `Scene.drillPick` for picking of multiple primitives
handle multiple ways of hiding primitives
changed test to check if setShow function is defined
fixed doc comment
Merge branch 'master' of https://github.com/gbeatty/cesium into multiPicking

Conflicts:
	CHANGES.md
	Source/Scene/Scene.js
Merge branch 'master' into multiPicking

Conflicts:
	CHANGES.md
fixed bad merge
code cleanup
sandcastle drill-down picking example
initial support for geometries
removed unused require
Merge branch 'master' into multiPicking

Conflicts:
	CHANGES.md
correctly handle geometry picking
Add Moon.
Merge branch 'master' into moon
Merge branch 'materials' into moon
Fix after merge.
Merge branch 'materials' into moon
Add tests.
Merge branch 'master' into moon