mikovtun

This PR adds device (CUDA) support for XC calculations with Unrestricted and Generalized Kohn-Sham references. LDA and GGA functionals are supported.

Running the test suite on device (#91) fails for the H3 test system (GKS GGA) when running on an NVIDIA RTX 3060 because the calculated `VXCx` and `VXCy` norms differ...