json: Print signatures for decrypt/verify
json: Print signatures for decrypt/verify

* gpgme-json.c (xJSON_CreateArray),
(add_summary_to_object, validity_to_string): New helpers.
(add_signature_to_object, add_signatures_to_object)
(add_signatures_object): New.
(op_decrypt): Handle verify_result.
(hlp_help): Mention decrypt.

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