Limit the number of neighbors and introduce a neighbor replacement policy

[atiselsts]

Currently, there is no limit how many neighbors a node may have. This does not reflect the reality of the embedded systems being simulated. There should be an optional configuration limit on the number of neighbors, and a policy for replacing them in case the number is reached.

[atiselsts]

The number of neighbors and routes now can be limited: #15

The support for replacement is not there yet.