OpenPGP: Detect and support Gnuk Token.

http://www.fsij.org/gnuk/
OpenPGP: Add Gnuk in pkcs15 emulation layer.
OpenPGP: Include private DO to filesystem at driver initialization.

In old implementation, the DOs which their access is restricted by
PIN (like DOs 0101 -> 0104) were excluded from the fake filesystem,
leading to that we cannot read their data later, even if we verified PIN.
PKCS15-OpenPGP: Declare DATA objects.

Begin to support read/write DATA object for PKCS-OpenPGP binding.
This object is used by TrueCrypt.
OpenPGP: Support erasing (reset) card.

Command: openpgp-tool --erase
OpenPGP: Support deleting key in Gnuk.
OpenPGP: Correct building Extended Header List when importing keys.
OpenPGP: Ignore "DATA NOT FOUND" error when retrieving pubkey.

When retrieving pubkey, a clean new Gnuk card returns error instead of "empty pubkey".
We will ignore this error, consider success with empty pubkey.