Refactoring for `brew list` - better handling of multiple parameters

The command `brew list`, by this patch, returns just a list of formulas.

By adding `--pinned` or `--multiple`, you can filter this list - but neither of those will change the format of the output.

By adding `--versions`, you will get a list of all versions of the formulae, included in the output, that are installed on your system. There is no highlighting of - or limit to - the version currently installed.