Keychain authentication backend

[emre]

The current patch for the Keychain voting was a temporary solution until we have a real Keychain authentication backend.

Keychain is not an accessible solution and it's limited to Chrome/Firefox afaik. Mobile browsers or other browsers don't have it.

Ideally, We should have SC and Keychain, both. A new repository including the Django Keychain Authentication Backend should be created, then it should be straight forward to set it up as an alternative authentication method to create polls and cast votes.