Update Model.cpp
Update Model.cpp

Test against document version 20001 (2.0) as used in test cases rather than version 2.4 (20302)
opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core