add utility function to add custom integrate style

    AddStyleHeader(${path} FIX)

endfunction(RegisterFixStyle)

function(RegisterIntegrateStyle path)

    AddStyleHeader(${path} INTEGRATE)

endfunction(RegisterIntegrateStyle)

function(RegisterStyles search_path)

    FindStyleHeaders(${search_path} ANGLE_CLASS     angle_     ANGLE     ) # angle     ) # force

    FindStyleHeaders(${search_path} ATOM_CLASS      atom_vec_  ATOM_VEC  ) # atom      ) # atom      atom_vec_hybrid