* jodawg.py: Add autojoin parameter.

* lib/configuration.py: Remove the base64 encoding/decoding (now in Encryption instead).
  Allow only '=' as separator to avoid problems with zmq URLs.

* lib/encryption.py: Create Key class and base64 handling.

* lib/overlay.py: Add Node join time, use new Key/Keypair interface for using raw and 64 keys
  at the right points in the code. Return at most 100 nodes for the overlay.
  Generate a node keypair even in stand-alone mode.

* lib/shell.py: Autojoin handling.

(NOTE: Doesn't work properly yet, investigating key encoding problems).