don't prevent removing contact iter in groupchat if there are pending event with an opened chat window. Fixes #4340

handle XEP-0203 (Delayed Delivery) and use it when forwarding unread messages via adhoc commands. Fixes #4347

use spec version instead of program version to determine which spec to use for notification-daemon. Fixes #4126

don't remove contact instance when we remove last event if a chat is stil opened, but when we close the window. Should fix #4272