Activity items identity themselves as `Image`

![screen shot 2014-08-19 at 16 48 09](https://cloud.githubusercontent.com/assets/109850/3968586/4c4af5ee-27b8-11e4-9fe4-4b8a5fcdf06b.png)

Rather than only covering content items (which didn't cover the user metadata bug), we should create a user, a couple of content items, a discussion and a group and list them all in search.