Add support for automatic permutation of the args of a candidate

[alexamici]

The signature of a function is an implementation detail and it would be nice it the candidate object could try different kind of permutations of args so that it can discover a matching callable independently if the detail of the signature.

For example:

• candidate(*args) could test [object(*perm) for perm in itertools.permutations(args)].
• Extend the above to use values in args for kwargs above len(args).