Imported libuser setup from nethserver-base. Refs #2492
Initialize admin account in LDAP. Refs #2492

If admin account already exists, preserve its password and uid number,
otherwise root password is imported.

The nsstest account is created with uid >= 501, to leave id 500 free
for admin.
nethserver-directory-user-modify: skip lusermod command if cn is empty. Refs #2492
Group/User UI modules: honour Removable prop. Refs #2492

The platform validator was not invoked in delete case, because the key
parameter is not submitted, but derived from the request URL path.
Additional sudo commands for adm group. Refs #2492
Migrate admin home directory. Refs #2492 #1655
Removed special case for admin. Refs #2492

Admin is record is of type user.
Change group memberUid attribute in LDAP directly. Refs #2492

Don't use libuser lgroupmod binary to manipulate group members. It
fails silently for empty members list.
Fixed executable permissions.
Create the predefined "locals" group. Refs #2492

The "locals" group always contains users defined into the local accounts database.
Check if group exists before signalling group-modify event. Refs #2492
Initialize admin and create default accounts at the end of yum transaction. Refs #2492

We temporarily rely on "runlevel-adjust" event, but a more specifc
event should be defined.