Modules tab

This PR implements a modules subtab, which allows the user to enable/disable modules as well as configure them.

![screen shot 2013-06-09 at 3 40 20 pm](https://f.cloud.github.com/assets/1118185/628910/24f7fa4c-d10a-11e2-9993-c07fce600864.png)

There is a known (major) bug in that the Apply button does not work. I think this is because the Object-Widget relation does not associate with the smart save buttons, since the smart save buttons are created in another widget. Ideas?