Implement notification emails for expiring and expired memberships

We'll send a notification email 30, 20 and 10 days before expiry,
and a final message when it actually expires.
Show the last 30 log lines and not the first 30 on membership page

Changes the sort order to be reverse, to make sure we show the newest
log info first. This also makes the cutoff after 30 actually make sense.
Add a special paragraph about exipring account for the first run

Since this is the first time we run the thing, lots of old members
will be expired. For this reason, add a special paragraph about it.
Do this as a separate commit so it can easily be reverted once the
initial around of email has been sent.
Revert "Add a special paragraph about exipring account for the first run"

This reverts commit ff1ba3bcdcb80d67a91ee16b519bf09eadf9ddec.