Improve the command line parser

[jlouis]

The command-line parser is currently quite weak and simple. It can be improved to handle many more commands and do much more than what is currently possible.

If you are feeling really adventurous, you should first play a couple of Infocom games, play with the inform interactive fiction creator tool, take a bit of craziness and implement "Adventure for a torrent". Less than this will do as well however :)