Use module names as menu titles

Cleans up the DS config menu to make it easier for devs to know what variables are used where. 

![screen shot 2014-11-07 at 9 46 02 am](https://cloud.githubusercontent.com/assets/1236811/4954469/d66cf5c0-668c-11e4-977d-a3f04f8a8b6e.png)

Third Party variables is the odd one here, mainly because it shouldn't live on the DoSomething Signup admin page, since the `communications team` needs access to set Third Party variables but should not have access to configure the DoSomething Signup variables.