* Add basic authentication in the server
A pattern for creating authentication methods is introduced, with three
authentication types defined:
none - no authentication
session - like the current session based auth used for user annotations
test - used to test the login/logout process end to end
The config endpoint now returns informations about the authentication, like if
the user is authenticated and their username. The redirect uri's for login and
logout are also returned if the authentication type requires login
This is the first a several PRs for authentication.
*. Update server tests to avoid hardcoded ports
test_api and test_nan_rest now use a common function for starting a test server,
than will initially choose a random port.
