Prohibit deletion of predefined profiles
Deletion of predefined profiles, including the default profile,
should not be allowed. Detect this case and raise an error.
Also update the predefined profiles collection to use namedtuple,
making it easier to access the various components.
Fixes: https://fedorahosted.org/freeipa/ticket/5198
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>