Rejig Organisation Pages

Use only one set of featured links rather than two. Toggle the difference between the two layouts using CSS rather than having a whole second list of links for each different homepage type.

Also in this change I have slightly modified the way organisation logos work. Before the large version would shrink straight down to the small version on mobile. I have updated this so that it now shrinks to the medium sized logo once the browser gets narrower than the full desktop layout. This means that the new position for featured links works with organisations with longer logos without breaking their logo.

Before/After:

![before-after](https://cloud.githubusercontent.com/assets/35035/4918790/81796f92-64f4-11e4-8bec-8c8971995890.png)

https://www.pivotaltracker.com/story/show/81853592