Merge branch 'eos_error_gizmo' into 'master'
Added equation of state check to Riemann solver. The currently implemented Riemann solvers only work with an ideal gas equation of state. I have added a compile time check to riemann.h that throws an error if the selected equation of state is not EOS_IDEAL_GAS. This way, it is impossible to compile GIZMO_SPH with a wrong equation of state. See merge request !224