Model.h   - Add a model type field to indicate identification of children model.   - Change getter functions so they all return target pointer.
Model.h
  - Add a model type field to indicate identification of children model.
  - Change getter functions so they all return target pointer.
James534/SubZero,Lrac/SubZero,mda-ut/SubZero,mda-ut/SubZero,James534/SubZero,mda-ut/SubZero,James534/SubZero