Boolean settings

# Changes
 - Adds descriptions to settings (to explain usage or special directions).
 - Add type to settings (defaults to `text`, optionally `boolean`)
 - Updates form to show a checkbox for boolean settings, and nicer formatting of settings admin view.

For review: @angaither

![screen shot 2014-12-16 at 10 38 31 am](https://cloud.githubusercontent.com/assets/583202/5456178/c0ea2ec4-850f-11e4-9c7d-552e5bb385d9.png)

![screen shot 2014-12-16 at 10 38 49 am](https://cloud.githubusercontent.com/assets/583202/5456182/c28088a0-850f-11e4-884c-83e29d9463ca.png)