Added 'prototypeFrom(...)' and 'copyToPrototype' methods to global Function, to simplify prototypal inheritance declarations, and reimplemented all 'class' declarations to suit. Draft implementation of ChoiceThingyRule walkSequence(...). Created allValid(...) function on CachingWalker for simplified validation logic.
Introduced initial example grammar and validation for Journey domain example.
An example verbatim from Joe Finney