Add ability to check membership status

[adam-p]

Right now there's no way for members to check on when their year of membership is expiring, and so know if it's time to renew (besides the reminder email). There's also no way to see if someone is a member at all (it's easy to forget if you've joined or not).

It would be nice to enable checking of membership status and renewal date.

Ideas:

• Field that takes an associated email address and sends an email to that member if they exist. But: This doesn't help if there is no such member (and we probably don't want to send email to every arbitrary email that's entered).