Checkbox CSS Class Improvement

The css class for the checkbox should be improved.

Boolean fields create a checkbox that needs an adjustment of either padding or margin. As you can see, it comes too close to other fields, and looks off.

![image](https://f.cloud.github.com/assets/595530/718699/48594bde-df6b-11e2-9748-0e20d7eec21e.png)