CMake: simplified installation of header files

src/CMakeLists.txt

src/TNL/CMakeLists.txt

src/TNL/Communicators/CMakeLists.txt

src/TNL/Config/CMakeLists.txt

src/TNL/Containers/Algorithms/CMakeLists.txt

src/TNL/Containers/CMakeLists.txt

src/TNL/Containers/Multimaps/CMakeLists.txt

src/TNL/Debugging/CMakeLists.txt

src/TNL/Devices/CMakeLists.txt

src/TNL/Exceptions/CMakeLists.txt

src/TNL/Experimental/Arithmetics/CMakeLists.txt

src/TNL/Experimental/Hamilton-Jacobi/CMakeLists.txt

...TNL/Experimental/Hamilton-Jacobi/Operators/CMakeLists.txt

.../Hamilton-Jacobi/Operators/Hamilton-Jacobi/CMakeLists.txt

...n-Jacobi/Operators/Hamilton-Jacobi/Eikonal/CMakeLists.txt

.../Operators/Hamilton-Jacobi/Godunov-Eikonal/CMakeLists.txt

...n-Jacobi/Operators/Hamilton-Jacobi/Godunov/CMakeLists.txt

src/TNL/Experimental/Hamilton-Jacobi/Solvers/CMakeLists.txt

...al/Hamilton-Jacobi/Solvers/hamilton-jacobi/CMakeLists.txt

src/TNL/Functions/Analytic/CMakeLists.txt