Previously the list of properties for each type of Graphics in the entity layer was different everywhere.  This made it quite difficult to compare the set of properties in the code vs the set of properties in CZML. I went through and reordered all these locations to have properties in the same order in each.

* The documentation for the constructor for each graphics type
* The content of the constructor (initializing `_property` and `_propertySubscription` to `undefined`)
* The public get/set properties
* The contents of the `clone` function for each graphics type
* The contents of the `merge` function for each graphics type
* The code assigning the values of properties in `CzmlDataSource`.

Also add some missing functionality to `CzmlDataSource`:

`box.heightReference`
`cylinder.heightReference`
`ellipsoid.heightReference`

`corridor.classificationType`
`ellipse.classificationType`
`polygon.classificationType`
`polyline.classificationType`
`rectangle.classificationType`