#6 Improve the robustness around ACLs

[Loďc Touraine]

when a user has no ACL associated, the webportal
management module doesn't behave properly.
When a module retrieves the user ACLs, when no acl is
available, it must print out a message such as "no
administrative rights are set for current user".
This behavior must be shared between modules relying
on ACLs.