refactor(developer): kmldmlc - rename `CompilerErrors` to `CompilerMessages`

Just wanted to rename this to make it clearer. Also added a prefix to
each message generator to indicate the type of message, as otherwise it
is not obvious within the compiler which messages are going to cause the
compiler to fail.

Note that the message generator function prefixes are Title Cased
whereas the message identifier constant prefixes are CAPS. I guess this
could be confusing but I think it works okay in practice.