change around and let ykpiv_sign_data() pad
add error messages
set version on the selfsigned cert
make get_length() take a const buffer
refactor transfer data so it can send 0 bytes
refactor reset to use ykpiv_transfer_data() instead
refactor pin-retries to use ykpiv_transfer_data()
refactor to ykpiv_transfer_data() for chuid setting
refactor change_pin() to use ykpiv_transfer_data()
stop exporting ykpiv_send_data()
refactor so ykpiv_sign_data() takes size_t input
drop unused code from delete_cert
drop apdu structure from tool