Changed remind syntax and added moar features to it. Also misc. fixes for remind

Someone may now be reminded up to 12 times, with an interval of minimum 15 minutes.
Also cleared up a couple of small issues. A user may stop the bot from reminding him/her by using "stop reminding me"

The remind table has been changed, you'll want to do "DROP TABLE remind;" before trying to use the new features. The old syntax is no longer valid.