Allow implicit state import from state transition declaration

[ImmutableOctet]

We currently require that all states be declared during the archetype parsing phase. This feature would allow importing additional states to the entity-descriptor if they're referenced as possible transition states in one of the regularly imported state definitions.

Example:

• Archetype declare States A & B
• State A has a rule declaration referencing State C if some condition is met. On runtime, this would not currently work.

Proposed solutions are as follows:

• Produce an error/assert indicating that an invalid state would be reached
• Ignore rules pointing to invalid/missing states (Probably best to detect this dynamically, since you could theoretically add to the entity-descriptor during runtime)
• Statically scan the names of all transition states, implicitly importing them due to being referenced in a rule. (This is problematic, since we don't have actual state paths, only state names)
• Allow states to declare their imports in a dedicated "states" or "imports" section. (This would also allow for exact paths to be used, rather than hoping we can directly resolve by state-name)
• Allow for an in-line import directive for the referenced state, allowing for an exact path to be provided.

I am currently undecided on which approach would be most effective, but I'm leaning towards an "imports" section for each state.

[ImmutableOctet]

This has been resolved as of #49.