Multiple Zoomfloppy support

[zoggins]

The UI sucks. :) One problem is there is no good way to detect which bus numbers have zoomfloppies, since using an incorrect bus value simply returns data from the "first" one. Also I thought about just setting a global with the adapter/bus value at detect drive time instead of determining it on each command, but had already gone down this path. Not sure if its worth just doing it once per detect drive or not.