Add CLI with these arguments

[bakustarver]

Allow the application to use such commands:
$ mkxp-z --gamefolder "/path/to/game/"
$ mkxp-z --vxacertpfolder "/path/to/vxacertpfolder/"

[Splendide-Imaginarius]

What's the use case for these specific two options? If the RTP folder is specifiable via command-line flags, why not all the other mkxp.json config options?