Overall behaviour should not have changed much except that there are now
3 different lists for lan, ipv6 and ipv6 nodes.
The DHT now uses a tree structure to store known nodes for close and friend
nodes.
It compiles but I barely tested it yet.
An index for replacement candidate is searched
in one lookup cycle for all types (bad, possibly bad, good).
Sorting of items has been removed (sorting logic can be substituted
by a maximum search).