Options::parse() should complain about unsupported options and should print help

This code:
```
int
main(int argc, char* argv[]) {
Options opt("Testcase");
opt.iterations(200);
opt.parse(argc,argv);
Script::run(opt);
return 0;
}
```
doesn't complain about bad arguments and doesn't print help.

It would be great if it would become a bit more user friendly.

Start at the Options::parse(argc, argv) entry point used in the issue's example and inspect how command-line arguments are currently handled. Exercise the example with an unsupported option and a help request; done means invalid arguments produce a complaint and help is printed when requested.

Written by the indexing model from the issue text.