Authorization

[hbcarlos]

Solves #44

For now, it is only a draft PR that solved some bugs with the Authentication and federated extensions.

Bug fixed:

• Remove dependency get_auth_config from create_guest.
• Support disabling extensions
• Reload federated extensions
• Adds field connected to users (I removed in my last PR, I thought wasn't necessary. It is)
• Changes users endpoint to collaborators and filters the active user
• Improves login page (Press enter to login by token)
• Dependency get_current_user selects user by token when using token mode

TODO:

• Add roles
  • ADMIN, READ, WRITE, RUN
• Allow registering anonymous users in token mode
• Create authorization dependency
• Add authorization dependency to all routes

[davidbrochart]

Some of the changes in a0cabe2 and fd93a16 have been merged in #124.

[davidbrochart]

@hbcarlos I think this PR was superseded by #206. If not, feel free to re-open.