add delete user functionality to lookup tool (bug 901783)

Delete sets a ```UserProfile```'s ```deleted``` attribute and deletes the one-to-one ```User``` model.

Also this logs  appropriately using ```ActivityLog```.

Can be done by anyone with ```AccountLookup:View```

**Delete section**
![screen shot 2013-09-17 at 2 53 05 pm](https://f.cloud.github.com/assets/674727/1161028/a175b1e0-1fe3-11e3-926b-cd842259921c.png)

**Delete modal**
![screen shot 2013-09-17 at 2 53 20 pm](https://f.cloud.github.com/assets/674727/1161029/a2be160a-1fe3-11e3-96fc-c40bc8fca489.png)

**Post-delete section**
![screen shot 2013-09-17 at 2 53 29 pm](https://f.cloud.github.com/assets/674727/1161032/a493d956-1fe3-11e3-868f-0caa43971f37.png)