Add support for destructured parameters in answers

[Osguima3]

I think this is a useful addition as it takes benefit of a language feature instead of calling the (arguably) more verbose option of calling the getArgument<T>(i) method on the invocation:

on { intResult(any()) } doAnswer { (i: Int) -> i * 2 }

instead of (still supported):

on { intResult(any()) } doAnswer { it.getArgument<Int>(0) * 2 }

[TimvdLippe]

Good suggestion! 1 small nit, the rest LGTM