Congestion control

Adding advanced congestion control mechanisms via a new congestionControlLayer class that replaces the default reliabilityLayer. Different RTO calculation mechanisms are available for the advanced congestion control layer: 
CoCoA (implenentation of draft-bormann-cocoa-02)
CoCoA-Strong (CoCoA, but only "strong" RTT measurements)
BasicRTO (RTO = RTT * 1.5)
Linux (Linux RTO mechanism)
Peakhopper (PH-RTO)

The advanced RTO algorithms can be activated by replacing the reliabilitylayer with one of these layers.
Also adds remote endpoints that store state information (RTT/RTO/etc.) and a manager for these remote endpoints.