Unscoped federated user-specific commands

A federated user can authenticate with the v3unscopedsaml plugin and
list the domains and projects she is allowed to scope to.
This patch introduces the new commands 'federation domain list' and
'federation project list'.
Note that for these commands -and plugin- to be available, the lxml
library must be installed.

Change-Id: I2707b624befcfb0a01b40a094e12fd68a3ee7773
Co-Authored-By: Florent Flament <florent.flament-ext@cloudwatt.com>