Merge branch 'diffusion'

examples/heat-equation/heatEquationSolver_impl.h

examples/heat-equation/tnlHeatEquationEocRhs.h

src/config/tnlParameterContainer.h

src/implementation/matrices/tnlCSRMatrix_impl.h

src/implementation/matrices/tnlChunkedEllpackMatrix_impl.h

src/implementation/matrices/tnlEllpackMatrix_impl.h

src/implementation/matrices/tnlMatrixSetter_impl.h

src/implementation/matrices/tnlMultidiagonalMatrix_impl.h

src/implementation/matrices/tnlSlicedEllpackMatrix_impl.h

src/implementation/matrices/tnlSparseMatrix_impl.h

src/implementation/matrices/tnlTridiagonalMatrix_impl.h

...lementation/operators/diffusion/tnlLinearDiffusion_impl.h

...mentation/operators/tnlDirichletBoundaryConditions_impl.h

...ementation/solvers/linear/krylov/tnlBICGStabSolver_impl.h

src/implementation/solvers/linear/krylov/tnlCGSolver_impl.h

...mplementation/solvers/linear/krylov/tnlGMRESSolver_impl.h

...mplementation/solvers/linear/krylov/tnlTFQMRSolver_impl.h

...lementation/solvers/linear/stationary/tnlSORSolver_impl.h

src/implementation/solvers/pde/CMakeLists.txt

src/implementation/solvers/pde/tnlExplicitTimeStepper_impl.h