Refactor Klawr::FCodeGenerator

Native wrapper functions are now generated by
Klawr::FNativeWrapperGenerator, C# wrapper classes are generated by
Klawr::FCSharpWrapperGenerator, and Klawr::FCodeGenerator just glues
everything together.

Klawr::FCodeGenerator::ExportClass() is still messier than I'd like,
but I'll get to it later.

Closes #9.
Start local variable names with a lower-case letter

I've tried sticking to the UE4 variable naming convention, but starting
every name with an upper-case letter regardless of whether it's a local
variable, a member, or a parameter is freaking annoying.