Bulk Add/Remove from Groups

Add the option to add or remove members from groups by email address. Instead of having to put in each email address one by one, we should be able to just paste in a list of email addresses and the action will be applied to all members with that email address.

An expansion on this would be that invites could be sent in bulk to any email addresses that are not yet members. And that members could be deleted in bulk the same way, etc.