Catch changed behavior in authentication routines

Future versions of libfreefare will set errno to EACCES if authentication to a
tag failed. See issue #20 in libfreefare for more details.

    http://code.google.com/p/libfreefare/issues/detail?id=20
Avoid a copy in freefare.UltralightTag.WritePage()
Implement first half of Mifare Classic functionality