After activating Vifib Facebook Server Extraction Plugin it is possible to use
facebook authorisation in Vifib.

Persons will be automatically created thanks to reusing REST API call, which has
already logic for Facebook user initial synchronisation.

Reuse 202 code, same like with request, to inform, that user has been allowed
to access, but not created yet.

Split internal and external ones.
Explain how to use Facebook authentication.

Otherwise not possible, because of slapos/slap/__init__.py doing
"from slap import *", and that "slap" module being shadowed by
"slapos.slap.slap.slap" class.

this optimisation is not valid.

This will reduce queries to server and improve performance for client.