#888 MatMatMatMylutSymbolic/Numeric isn't actually implemented in Petsc; I...

#888 MatMatMatMylutSymbolic/Numeric isn't actually implemented in Petsc; I have issued a ticket and add a warning in HappyHeart.

Sources/ThirdParty/Wrappers/Petsc/Matrix/MatrixOperations.hpp

@@ -243,6 +243,8 @@ namespace HappyHeart
              *
              * \param[in] invoking_file File that invoked the function or class; usually __FILE__.
              * \param[in] invoking_line File that invoked the function or class; usually __LINE__.
+             *
+             * \attention Currently not working due to lack of implementation in Petsc; a ticket has been issued.
              */
             template
             <
@@ -278,6 +280,8 @@ namespace HappyHeart
              *
              * \param[in] invoking_file File that invoked the function or class; usually __FILE__.
              * \param[in] invoking_line File that invoked the function or class; usually __LINE__.
+             *
+             * \attention Currently not working due to lack of implementation in Petsc; a ticket has been issued.
              */
             template
             <