Mailbomb subscription fix!

[anarres]

I fixed it so you no longer get bombarded by emails when you subscribe to a thread and there are lots of replies.

Now, once an email has been sent for a reply no new emails will be sent for that thread until you revisit the forum.

Please ask questions and report any issues here, for example if you still get multiple emails or if you don't get any.

Also, the Subscriptions page has been changed again. There are now icons for read/unread threads and the category/forum info isn't listed with each entry (it is a tool tip instead).

Edit: Unstickied