Feature/simple hyperviscosity mrh resolved

in hyper.f90:

addition of a simple 3-D hyperviscous filter based on gs2s internal kperp2. currently experimental, but expected to replace the current hyperviscous models which are 2-D and do not respect continuity along the field line, and are not parallel in kx ky * missing code_dt added -- makes D_hyper3D a rate