Alias support

[matejak]

Some arguments can have long descriptive names s.a. --add-another-value, so it can be convenient to add a long, but abbreviated option (i.e. alias) s.a. --aavalue.

[yodapotatofly]

This would definitely be usefull to me. my script support installing dependencies on the fly with the --install-all option. I'd like to add a shorter --iA option.

In the same spirit, --install-all is actually a shorctut for --install-this --install-that, so it would be awesome it this use case could be supported

As of today, I have to manually edit the parsing and help fonctions to add those