Tell clients of model object classes permitted by graph commands.

[mtbc]

The CLI graph commands' --list provides a list of classes that can be explicitly targeted but it is not exhaustive, for example, it may name a superclass instead of enumerating each subclass. Further, other options like --include or --duplicate can correctly accept a wider set of classes, anything that is noted in an initialized GraphPathBean's classesBySimpleName. It could be helpful to make that set of class names available to clients, perhaps even by doing codegen that generates the same.