added plot mesh

mlmc/src/pdesolver/PDESolver.hpp

 #ifndef PDESOLVER_HPP
 #define PDESOLVER_HPP
 
-// Assembling imports
 #include "IStochasticDummyAssemble.hpp"
 #include "Sample.hpp"
 
@@ -91,7 +90,7 @@ protected:
   }
 
   void plotSolution(SampleSolution &solution) override {
-    // plot meshes?
+    mpp::plot_mesh(solution.U.GetMesh());
   }
 
 public: