Certify key.

In-place editing with a popup if user is allowed in app config file.
User must of course manage at least a private key. User identities of
target key may be selectively chosen. Optionally, certification may be
exportable and non-revocable.

WTAPPROOT/K7/k7config.json

@@ -4,6 +4,7 @@
             "canImport" : true,
             "canDelete" : true,
             "canEditOwnerTrust" : true,
+            "canEditUidValidity" : true,
             "privKeyIds" : [
                 "FullKeyId1",
                 "FullKeyId2"