Type test: Add validation test for Ref of function. Drop ambiguous test.
Type: Refactor Table.

* On bad type declaration, throw LlamaBadTypeError.
* Split type processing into functions for readability.
Type: Rename variable to convey meaning.
Type: PEP8-ing.
Type test: Improve coverage and readability of Validator tests.
Type test: Validator will report errors via exceptions.
Type: Add LlamaInvalidTypeError exception
Type: Raise LlamaInvalidTypeError exception on bad type.
Tests: Add class to abstract parser memoization.
ParserDB: Clear previous logger state on each call.
Tests: DRY using parser_db.