[UP-4296] Add support for a 6 column layout.

https://issues.jasig.org/browse/UP-4296

Screens:
Large screen - show all 6 columns...
![6col-max](https://cloud.githubusercontent.com/assets/7871998/5096712/dd4fee4e-6f31-11e4-8b97-ab9c8924e772.png)

Collapses to 3 columns...
![6col-3x3](https://cloud.githubusercontent.com/assets/7871998/5096713/e0207d64-6f31-11e4-9dca-beeda87d5f0a.png)

Collapses to 2 columns...
![6col-2x3](https://cloud.githubusercontent.com/assets/7871998/5096717/e29cedac-6f31-11e4-9f00-eab71e90910a.png)

Collapses to 1 column
![6col-1x6](https://cloud.githubusercontent.com/assets/7871998/5096721/e4ed8896-6f31-11e4-90c9-9aac0c81463c.png)