json: Add op_createkey
json: Add op_createkey

* src/gpgme-json.c (hlp_createkey, op_createkey): New.
(process_request, hlp_help): Add it.

--
This uses an unrestricted context for now until

GnuPG-Bug-Id: T4010
is implemented in GnuPG.

gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme