Use new Context::setExpire to set expiration dates.

If no subkey is found (wrong fpr) or not provided, the expiry time of 
the key is set instead.

setExpire() allows to expire all subkeys at once. Not implemented here.

Requires GPGME >= 1.15.0.

KeyEdit.h

@@ -58,7 +58,7 @@ private:
      */
     void FillOwnerTrustCombo(WComboBox * cmb, bool keyHasSecret);
     void EditUidValidity();
-    void SetExpiryTime();
+    void SetKeyExpiryTime();
     void AddOrRevokeUid();
 
     /**