Cmdline: Remove now obsoleted 'config' option.
RegistryManager.Instance() now always requires a path.

I'm really not so sure about this change. It means we no longer have
problems where we try to access the registry before we have a
current install, but it is a monumental pain in the ass.

Luckily, this commit should also be easily reversable.
CmdLine: Add back `--kspdir` option.

Holy smokes this works again. I have dreamed of this moment.