Merge OTMeCpp back into OT_ME

To facilitate the conversion from ChaiScript to C++ two different OT_ME implementations were created. OtMeChai and OtMeCpp. The first one was removed a while ago upon completion of the C++ conversion. 
So now the C++ version can be folded back into OT_ME thereby eliminating an extra indirection that is no longer necessary. And in the process removing OtMeCpp.
@BugFreeSoftware to create a separate scope for every `case` is not necessary.