Make Polyline and Path use materials

Get rid of most invidual properties and use materials instead
Add PolylineOutline and PolylineGlow materials.

This goes along with AnalyticalGraphicsInc/cesium/pull/1904

One possibility is to have a PolylineMaterial.jsonschema instead of using Material.jsonschema.  This will allow us to restrict the materials polylines can use down to a specific set.  What do you guys think?

EDIT: I decided `PolylineMaterial.jsonschema` was a good idea so I added that (see the second commit below for details).