Works on restart (introduce a restartManager to manage the read/write

operations allowing to have only one method in the objects). Warning
restart methods still to be defined for dG3D and msch IPVariables. 

Geo/SPoint3.h

@@ -44,6 +44,8 @@ class SPoint3 {
     if (P[2] < p.P[2]) return true;
     return false;
   }
+  const double* data() const{return P;}
+  double* data() {return P;}
 };
 
 inline SPoint3 operator + (const SPoint3 &a, const SPoint3 &b)

Geo/STensor3.h

@@ -220,6 +220,8 @@ class STensor3 {
   inline double get_m13(){ return _val[2]; }
   inline double get_m23(){ return _val[5]; }
   inline double get_m33(){ return _val[8]; }
+  inline const double* data() const {return _val;}
+  inline double* data() {return _val;}
   void getMat(fullMatrix<double> &mat) const
   {
     for (int i = 0; i < 3; i++){

Geo/SVector3.h

@@ -89,7 +89,8 @@ class SVector3 {
       return 2;
     }
   }
-
+  const double* data() const {return P.data();}
+  double* data() {return P.data();}
 };
 
 inline double dot(const SVector3 &a, const SVector3 &b)