Non-bonded NxN PME kernels

Tests the non-bonded NxN PME kernels (several CPU + GPU versions).
For the x86 SIMD kernels the combination rule matters: geometric here.
For the x86 SIMD kernels there is optimization for atoms with/without
LJ or charge, therefore this system has a water and united-atom hexane slab.

This test copies the setup of complex/nbnxn_pme
