- if knownNodes grows to 20000, instead of ignoring new nodes, forget
the 1000 oldest ones
- drop connection after sendaddr if too many connections, even if it's
an outbound one
- if maximum total connections are lower than maximum outbound
connections, active bootstrap provider mode
- in this mode, check all addresses received before announcing them
- so basically it only annouces those addresses it successfully
connected to
- saveKnownNodes replaced the repeated pickle.dump
- with knownNodesLock instead of acquire/release
- outgoingSynSender had an unnecessary loop during shutdown causing
excessive CPU usage / GUI freezing
- rearranged code to reduce cyclic dependencies
- doCleanShutdown is separated in shutdown.py
- shared queues are separated in queues.py
- some default values were moved to defaults.py
- knownnodes partially moved to knownnodes.py
