More memory leak fixes.

Broke another circular pointer dependency by turning shared_ptrs into weak_ptrs. Added code to tidy up CFI to plug those leaks. Added virtual destructor to NodalUtil so that the derived classes can be deleted.

library/LibUtilities/Foundations/NodalUtil.h

@@ -83,6 +83,7 @@ typedef std::shared_ptr<NekMatrix<NekDouble> > SharedMatrix;
 class NodalUtil
 {
 public:
+    LIB_UTILITIES_EXPORT virtual ~NodalUtil() = default;
     LIB_UTILITIES_EXPORT NekVector<NekDouble> GetWeights();
     LIB_UTILITIES_EXPORT SharedMatrix GetVandermonde();
     LIB_UTILITIES_EXPORT SharedMatrix GetVandermondeForDeriv(int dir);