Added email spamming.  #27

Added a page that lets you select a milestone and closed/open status and send a reply to all desk cases that match.
The email isn't configurable right now, but that shouldn't be a big deal.

I'm getting unnamed validations errors with cases that came in from email.  I suspect that's because they have no smtp server and can't send out.  Otherwise I have no idea why that's the pattern.

TODO
1. Auth.  We should not publish a URL that lets anons spam our users.  Will probably have to be an $ENV var unless we go the drupal route.
2. Duplicates.  Should duplicate messages be withheld?  If so, I'm not sure how.