#31 force root class to be a FakeRootClass

[Stephen Fink]

I'd like to enforce that the declaring class for an AbstractRootMethod be a FakeRootClass (or some suitable new AbstractRootClass, if necessary). This would allow
us to eliminate an ugly cast in the body of the AbstractRootMethod constructor.

The CAST JavaScript layer doesn't use FakeRootClass here; would need to enhance cast.js to have appropriate FakeRootClass support, in order to make this change.