In some foodcoops it is possible that ordergroups make a break. During that
they e.g. pay reduced or no membership fees and do not need to do work for
the foodcoop. This new fields make this visible to all members.
Messagegroups are a new kind of group. Every user can join and leave such a
group on her own. They are useful to create topics for mails.
E.g. if there is a weekly newsletter we can create a new messagegroup for
it and every user which is interested in receiving the newsletter can join
the corresponding group.
