Update dashboard css

- Align table columns (when having multiples admin groups)
- Removes bottom shadow from buttons with ``.btn-link`` class

**Before**
![before](https://cloud.githubusercontent.com/assets/663607/2695314/16d421da-c3d4-11e3-80f2-ac9b4624c0aa.JPG)

**After**
![after](https://cloud.githubusercontent.com/assets/663607/2695313/16bce4ca-c3d4-11e3-9f68-66988cd8264a.JPG)