rt-dump-metadata love

- fix a bug on dumping UserDefined groups (One should never dump other
  than UserDefined groups IMO)
- Add some extra options:
    -l: limit user metadata to privileged users
    -s: skip disabled objects
- make the dumping of ACL's work without references to Principal IDs
- Add Applies-To information about CF's.
  NB:  This still leaves in a small bug: Unused CF's on the sending side
       turn into globally applied CF's when importing that.
       Not a huge deal IMO.
  NB2: In 4.2 this structure is renamed to ApplyTo together with
       a field named LookupType. Ignored for 4.0.