Feature: Declarative hooks for watching and other "WhileInState" operations

[n8allan]

This avoids the problem that can arise when using, for instance, WatchOtherWhileInState on a superstate, where if the developer forgets to explicitly pass the superstate to the "inState" param, the assumption is made to watch on the sub-state actually being transitioned into, which causes the watch lifetime to be only for the sub-state, not the intended superstate.