(New) AMR criteria: on by default with sensible values or off to avoid accidental refinement?

[ykempf]

In testing I was "surprised" to get default-valued active vorticity refinement when it wasn't called for in the cfg. We had decided that at least alpha1 and 2 should be on by default with sensible values when refinement is active. As we're moving towards more varied and somewhat specific criteria (e.g. targeting the foreshock with anisotropy) I'd advocate for us to change tack and not make all of them active by default. Maybe alpha1 and 2 could be on by default, but vorticity and anisotropy maybe should be off by default, albeit with sensible default values for their parameters.