#59 Communication layer overhaul

[Patrick Ostie]

Trough the introduction of GUIDs the communication layer needs to be revamped.
The old pending-, queuedMessages concept doesn't work anymore or is obsolete.
A new (simpler) concept (to stop sending redundant messages) needs to applied.
An approach which handles this automatically on receipt/sending of messages would be preferable.

[Patrick Ostie]

Pending and received Messages works again.
This is now simpler implemented in the Mediator.
There is still work to be done, to automate this step on receive or on send.