scd:nks: Add framework to support IDKey cards.
* scd/app-nks.c (NKS_APP_IDLM): New. (struct app_local_s): Replace NKS_VERSION by the global APPVERSION. (do_learn_status): Always send CHV-STATUS. (find_fid_by_keyref): Basic support for IDLM only use. (do_learn_status_core): Ditto. (do_readcert): Ditto. (verify_pin): Ditto. (parse_pwidstr): Ditto. (do_with_keygrip): Ditto. (switch_application): Ditto. (app_select_nks): Fallback to IDLM.