Support of natural vararg

[mathze]

As found out in #1 the straight forward way of vararg support didn't worked and a 'workaround' was implemented.
This task is for further investigation on that field and hopefully find a way to make it work.
Motivation:
It is more natural to use fun aFunction(vararg values: String) instead of fun aFunction(@KwdArg(kind=ParameterKind.VARARG) values: List<String>?).
Beside the aesthetic aspect the former is less error prone, much shorter and better readable.