mini/x2gobroker-ssh-mini: add missing hostname/IP and port autodetection.

The manpage mentioned an autodetection feature, but it wasn't present in the code. Seems some of my local git repos weren't in sync. Manually adding this chunk of code from my local repo that seems to contain the newest version, after changing path names/file names to the new convention (x2gobroker-ssh-mini instead of x2go-mini-ssh-broker)