Improve SSH logging

[Darkren]

Notices this piece of code in therealssh:

func debug(format string, v ...interface{}) {
	if !Debug {
		return
	}

	log.Printf(format, v...)
}

And it's actually being heavily used. I suggest that we improve logging here and switch to more common solutions which support log levels like it's done in the other parts (i.e. DMSG)