Refactor the anniversary code; adds a view that mails out anniversary announcements

To make use of this a few new keys need to be added to the anniversary feature config. These tell morgue where to email the announcement and what to set the From: headers to.

```
    { "name" : "anniversary",
      "enabled": "on",
      "navbar" : "on",
      "mailto" : "outage-announce@yourco.com",
      "mailfrom" : "Morgue <morge@yourco.com>"
    },
```