Client to queue request messages to server and resend them when needed

[mshabarov]

Client should queue all send requests and only send the next after previous has received a response.
Server always responds to the client message.

• Create a queue for send(payload) requests that is then cleared by sendInvocationsToServer
• First input to the queue is sent immediately, but only removed when the response is received
• Add a timeout for resending the message if no response is gotten for an x amount of time.

We already have the ServerRpcQueue that queues invocations to be sent and are sent in order when MessageHandler has handled json and runs processMessage or in handleJSON when old package is received

Looking at components at least SpreadSheet uses send directly:

        if (payload != null) {
            getLogger().info("Re-sending last message to the server...");
            getConnection().getMessageSender().send(payload);
        } else {