(feat) Added getter for unknow nodal index

The getter is added in the Solver

dart/src/wSolver.h

@@ -80,6 +80,8 @@ public:
     virtual Status run();
     void save(tbox::MshExport *mshWriter, std::string const &suffix = "");
 
+    int getRow(int i) const { return rows[i]; };
+
 protected:
     void computeFlow();
     void computeLoad();