Kokkos: The Computation of The Element Matrices of a 3D Finite Element Discretization of the Laplacian on a Mesh of Tetrahedral Elements

1. Make sure Makefile points to the correct Kokkos directory
2. To target CPU, build with make -j4 KOKKOS_DEVICES=OpenMP
3. To target GPU, build with make -j4 KOKKOS_DEVICES=Cuda