Absent CREW_OBJECTs should now be counted

 calculate_crew_percentage now accepts a second
 parameter, which contains a delta to be applied
 to the ship's crew level before percentage
 calculation. This is used currently to account
 for CREW_OBJECTs (Syreen Song crew, Ur-Quan
 fighters, etc) which should be counted as crew
 for the purposes of scoring. Currently, active
 Syreen Song crew are always included for the
 purposes of scoring, as well as any Ur-Quan
 fighters or Orz marines that belong to the
 ship being evaluated.