Class Animation: Document alternative object hash based signature. Fixes...

... #101 - Document children option for class animation methods.

There might be a better way to do this without duplicating. There are 16 lines documenting the duration/easing/complete properties in animation-signature-options.xml and class-animation-argument-options.xml that are duplicated.

I couldn't come up with a good way of sharing a collection of properties and I'm not sure whether it's worth it.