- 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
- it didn't shutdown correctly
- it didn't handle exception correctly (however, if I understand
correctly, this will never be triggered if using blocking get, so it
doesn't affect PyBitmessage)
- flushing size check changed from 1 to 0 (I don't know why it was 1)
