Update usart_comm.c

Make response for get config the same length on success and error
Make ACK's only happen once

An ACK_BAD or ACK_GOOD is final and definite.
Implement factory reset comm scheme

Still need to impl the reset itself
Relock responds ok if already locked

As far as client cares, relock successfully finished. The drive is locked after the call.
Merge branch 'master' of github.com:cellasecure/cella-avr32-firmware
Merge pull request #6 from palarson/master

Working script and command scheme picture
mount/unmount reliable
mount/unmount reliable
FAT format working
FAT format working. fixes #8
Merge branch 'master' of https://github.com/cellasecure/cella-avr32-firmware
Factory reset initialization tool. Closes #7
slight refactor, config files added
Multi-factor authentication. Closes #11
Reconfigured for BT comm
Merge branch 'master' of github.com:cellasecure/cella-avr32-firmware