Starting to implement

So, Gajim can basically send and request acks to a server. I haven't through fully tested it, but I will leave that for latter. Right now I'm focusing on resumption, which is harder because it changes the way Gajim connects to the server if it knows that resumption is accepted by the server.

For efficient acking the specification shows this example:

C: <enable/>
S: <enabled stanzas='5'/>
C: <message/>
C: <message/>
C: <message/>
C: <message/>
C: <message/>
C: <r/>
S: <a h='4'/>
C: <message/>
C: <message/>
C: <message/>
C: <message/>
C: <message/>
C: <r/>
S: <a h='9'/>

Which I find very weird that the server is the one who gets to set the interval in which the requests are sent. Since both, the sever and the client, can send and receive acks at any time, it doesn't makes sense that the server cares or has any say on how often the client sends acks.

So I made the judgment call to ignore this for now and let Gajim decide when it wants to send acks.