Collapse the domain form options fieldset

Here's the patch.

It might be helpful to explain why I needed this patch: in my site some content types (let's call then type A) can belong to one or more domains and other content types (type B) belong to the main domain only. Ideally I would like to be able to show the domain options fieldset for type A nodes only. Type B nodes would always be assigned to the main domain by default, so ideally the domain options fieldset wouldn't be shown at all for those.

Does the module allow that configuration currently? I didn't find a way to do it with the module's existing permissions, so to make life a little easier for the site's content editors, I came up with this very simple patch. I would love to be able to show or hide domain options per content type, but I don't know the module well enough to attempt that level of customisation.