UsbDevice list dialog on OK

If everything is fine, open a dialog showing attached USB devices. On selecting
one of these devices, try to open it. On success, extract its file descriptor,
put it in the DcData object and pass it on to the ImportProgress activity,

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>