added Get_Pressure_from_DE to Exact_cuda
added Get_Pressure_from_DE to Exact_cuda

cholla-hydro/cholla,evaneschneider/cholla,cholla-hydro/cholla,evaneschneider/cholla,cholla-hydro/cholla,evaneschneider/cholla,evaneschneider/cholla,cholla-hydro/cholla