Fix for issue #134 (Disallow numeric enum members)

Added a check in the parser to flag all numeric enum member names as errors. As mentioned in the comments of #134, this breaks a lot of the test cases. In some cases, where failing a test case for this error did not seem in the spirit of the test, I rewrote the test and in one case I even removed a test that no longer made any sense. In addition there were a few baselines that needed to be changed.
Sounds good!