- changed Probe class behaviour so that it will not throw an

- changed Probe class behaviour so that it will not throw an
       exception on Device Busy (-EBUSY) but instead
       log the error in an internal array and keep going.
       This makes it possible to use btool and barrybackup
       with two devices plugged in at the same time.
       BACKWARD COMPATIBILITY NOTE: this changes initializaion
	       behaviour, but in practice, it should only
	       make applications look more capable, not less.
- updated btool to show errors logged by Probe