Split fromString method for big enums that would otherwise not compile

[lhns]

With big enums the generated fromString methods exceed the allowed method size and won't compile.
This PR splits the fromString method into multiple private methods with 500 lines each.

[Th3Falc0n]

Had the same problem, supporting this fix.

[lhns]

I don't know why the travis builds timed out.

[eed3si9n]

Sorry about the late response. I'm merging this now.

[mirelon]

PartialFunction[Any is causing a compile error when parsing Seq[String]

non-variable type argument String in type pattern Seq[String] (the underlying of Seq[String]) is unchecked since it is eliminated by erasure

scalaxb 1.7.4 is OK
scalaxb 1.7.5 is failing

Will try to create a test case.

[lhns]

That is a warning and you have -Werror or -Xfatal-warnings set right?
Weird that the compiler doesn't warn about this before the commit.