Kokkos Example: Simple finite element integration of a vector valued function on a box.
Mapping of nodal coordinates can be skewed. Linear or quadratic elements. Lumping of element integral to nodes via atomics or second pass gather-sum functor. Integral of function has analytic answer for verification. TODO: Clean and add extensive comments. TODO: Build with cmake and add to cmake test. Fix create_mirror_view to allow mirroring views with 'const' data type.