DynamicPositionProperty and DynamicVertexPositionsProperty cleanup

1. Remove `getValueCartographic`
2. Rename `getValueCartesian` to getValue.
3. Remove `getValueRangeCartesian` since it is unused.
4. Also start to clean up DyanmicDirectionsProperty.
Merge branch 'geojson' into dynamicScene-cleanup
Merge branch 'geojson' into dynamicScene-cleanup
Merge branch 'geojson' into dynamicScene-cleanup
Remove getValueSpherical and make it the default result of getValue for DynamicDirectionsProperty.

In reality, I might abandon what I've done so far in favor of a new approach.
Merge branch 'master' into dynamicScene-cleanup
Some boilerplate code for a new property system that's not at all ready yet.
Merge branch 'master' into dynamicScene-cleanup
More Property prototyping.
Merge branch 'master' into dynamicScene-cleanup
Merge branch 'master' into dynamicScene-cleanup

Conflicts:
	Source/DynamicScene/DynamicConeVisualizerUsingCustomSensor.js
Specs for ConstantProperty and TimeIntervalCollectionProperty.
Merge branch 'master' into dynamicScene-cleanup
Add a simple CompositeProperty
Start of SampledProperty, no where near done.
Merge branch 'master' into dynamicScene-cleanup
Ongoing SampledProperty work.
Start major overhaul of CZML processing to use new property system.
Merge branch 'master' into dynamicScene-cleanup
Remove almost all DynamicProperty usage.

DynamicPositionProperty is still using it, but that will change shortly.