Improvement: add or extend membership

It would be a good feature if one could assign certain memberships to certain members or all members for a given time. E.g. extend membership for all paying members for a few days (cause of server problems or whatever) or e.g. assign payed membership to all members for a certain time as kind of "preview".

This would be easy enough to add to the members menu or the membership menu in the admin.  Create a form and have it update the membership expiration.  We could probably hash out the code for this. The date is stored by Dolphin in the form of 0000-00-00 00:00:00, with is a DATE and TIME for the membership to expire.