Sub-group display off when multi-site enabled

To reproduce:

• Enable multisite (you don't have to configure multiple sites, just enable it)
• Create a sub-group
• On the "manage groups" page, click the triangle to reveal the sub-group

The problem is that the js is hard-coded to expect a certain number of rows in the table. I'm wondering if we could take a more flexible approach - perhaps give each cell in the table header a unique class based on the field and have the js read that info.