Refactoring the eikonal solver.

examples/hamilton-jacobi/HamiltonJacobiProblemConfig.h

examples/hamilton-jacobi/HamiltonJacobiProblemSetter_impl.h

examples/hamilton-jacobi/HamiltonJacobiProblem_impl.h

src/functions/CMakeLists.txt

src/functions/tnlFunctions.h

src/operators/hamilton-jacobi/tnlEikonalOperator.h

src/operators/hamilton-jacobi/upwind-eikonal/upwindEikonal.h

...ors/hamilton-jacobi/upwind-eikonal/upwindEikonal1D_impl.h

...ors/hamilton-jacobi/upwind-eikonal/upwindEikonal2D_impl.h

...ors/hamilton-jacobi/upwind-eikonal/upwindEikonal3D_impl.h

src/operators/tnlNeumannBoundaryConditions.h

src/solvers/ode/tnlExplicitSolver.h

src/solvers/ode/tnlExplicitSolver_impl.h

src/solvers/ode/tnlMersonSolver_impl.h

src/solvers/ode/tnlODESolverMonitor.h

src/solvers/ode/tnlODESolverMonitor_impl.h

src/solvers/tnlIterativeSolver_impl.h