Added meaningful not_found exception messages
fixed unbounded value "res.constr" in line 1440
changed to state_var_of_original_name
Flag for input file to interpreter
Flag for number of steps
Fixed flag --interpeter_steps
Merge remote-tracking branch 'kind2_master/PaulMeng-kind2-interpreter' into interpreter

Conflicts:
	src/flags.ml.in
fixed transys.state_vars to return all variables