(feat) Add tol setters in Solver

dart/src/wSolver.h

@@ -81,6 +81,8 @@ public:
     void save(tbox::MshExport *mshWriter, std::string const &suffix = "");
 
     int getRow(size_t i) const { return rows[i]; };
+    void setRelTol(double const rtol) { relTol = rtol; }
+    void setAbsTol(double const atol) { absTol = atol; }
 
 protected:
     void computeFlow();