remove physics namespace

Processes/NullModel/NullModel.cc

-#include _Physics_NullModel_NullModel_h_
+#include <Processes/NullModel/NullModel.h>
+

Processes/NullModel/NullModel.h

 #ifndef _Physics_NullModel_NullModel_h_
 #define _Physics_NullModel_NullModel_h_
 
-namespace physics {
+namespace processes {
 
-  namespace processes {
+  class NullModel {
 
-    class NullModel {
-
-    public:
-      NullModel();
-      ~NullModel();
-
-      void init();
-      void run();
-      double GetStepLength();
-    };
+  public:
+    NullModel();
+    ~NullModel();
     
-  }
+    void init();
+    void run();
+    double GetStepLength();
+  };
+  
 }
 
 #endif