Coherent plan for GroupStatus.is_active

[adehnert]

The GroupStatus?.is_active field seems to be used for three things:

• controlling str(GroupStatus?)
• determining whether a group is yellow or red in the group list page
• controlling whether a group appears in the output of util/export_website_groups.py

This is sorta a silly mish-mash, and should probably be made somehow more consistent.

[adehnert]

In commit c4282e232b5a9a48b9c6d5acb3d0e7c84d77321c, I decouple is_active from at least the first use, since it seems rarely desired:

Author: Alex Dehnert <adehnert@mit.edu>
Date:   Mon Jun 3 05:57:56 2013 -0400

    Take is_active out of str(GroupStatus) (ASA-#230)