reset so that a new probing period can produce more up-to-date
estimates. Added a congestion mechanism whereby a neighbor can be
marked as being congested for a period of time, during which the ETX
for the neighbor will be artificially inflated.
* Loop detection and untangling. Now uses in-band loop detection that
works.
* Link quality estimation. Now starts with a conservative /
pessimistic estimate for new links.
* Retransmissions. MAC layer and network layer retransmissions are now
decoupled.
* Loss handling. Deals better with losses now.
* Concurrent applications. Each connection now maintains its own
neighbor table with separated cost to sink estimates for each
connection.
