Added some minor documentation

apps/openmw/mwworld/refdata.hpp

@@ -44,6 +44,9 @@ namespace MWWorld
             ESM::Position mPosition;
 
         public:
+            /// @param cr Used to copy constant data such as position into this class where it can
+            ///           be altered without effecting the original data. This makes it possible
+            ///           to reset the position as the orignal data is still held in the CellRef
             RefData(const ESMS::CellRef& cr) : mHasLocals (false), mEnabled (true),
                                          mCount (1), mPosition(cr.pos) {}