Run-time error checking of caching

[artgoldberg]

When caching, species populations must not be modified in between eval() calls. Detect caching errors with a dynamic_model.cache_violation FSM with transitions:

initial: INIT
update species pop:
	INIT -> POP_UPDATED
	POP_UPDATED -> POP_UPDATED
	EVALED -> EVAL_N_UPDATED
	EVAL_N_UPDATED -> EVAL_N_UPDATED
	UPDATED_N_EVALED -> EVAL_N_UPDATED
eval:
	INIT -> EVALED
	POP_UPDATED -> UPDATED_N_EVALED
	UPDATED_N_EVALED -> UPDATED_N_EVALED
	EVAL_N_UPDATED -> ERROR