./cake --types should also show exceptions and abbreviations

Some identifiers that are within lexical scope don't appear in the output of ./cake --types. It's possible that some things will always be missing with the current approach (based on the type inferencer's environment) but I think we should at least be able to get exceptions and type abbreviations. I think the way to address this is to add more functionality to the definition of `infer$inf_env_to_types_string`.