scd:nks: Support the Telesec ESIGN application.
* scd/app-nks.c (find_fid_by_keyref): Disable the cache for now. (readcert_from_ef): Considere an all zero certificate as not found. (do_sign): Support ECC and the ESIGN application.
This allows me to create qualified signatures using my Telesec card.
There is of course more work to do but this is the first step.
Note: The design of the FID cache needs to be reconsidered. Until
that the lookup here has been disabled. The do_sign code should be
revamped to be similar to what we do in app-p15.
Backported-from-master: 07eaf006c2763a6b40d2734b1c6704da466e0ed0