- 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)
- minor refactoring, made it into singleton instead of a shared global
variable. This makes it a little bit cleaner and moves the class into
a separate file
- removed duplicate inventory locking
- renamed singleton.py to singleinstance.py (this is the code that
ensures only one instance of PyBitmessage runs at the same time)
