- 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
- fixes errors introduced in the earlier refactoring
- more variables moved to state.py
- path finding functions moved to paths.py
- remembers IPv6 network unreachable (in the future can be used to skip
IPv6 for a while)