Lint contrib/generate.py.

Avoid 'unused variable' and don't redefine builtins.
Scallion solib: Add support for bridge auths, relays and client.
Scallion plugin: Add support for bridge authorities.
Add support for generating a Tor network with bridge authorities.

NOTE: Needs more for bridge relays and clients running with bridges.
Merge pull request #178 from ln5/bug113

Bug113