Networking reorganization refactor

## Networking/P2P code reorganization/refactor notes.
- All Peer Connection related classes will go to a module called 'connection'
- All Transport related classes will go to a module called 'transport'
- Bye bye crypto2crypto.py and p2p.py, hello connection.py and transport.py
- All static functions found on these classes that are not core to what they do but to utilitarian tasks that can be reused by other classes will be moved out of these classes and into utility modules (crypto_util.py), for example, cryptographic key handling functions don't belong on transport classes if they don't have any mention of self._properties in them, other classes can reuse, reducing the possibility of having a bug in multiple places.
- kademlia.py was unused, there was only an exception class (TimeoutError) that was moved to the routingtable module.
- major import cleanup. only importing the necessary, no unused imports.