Activity stream pagination

Pagination on activity streams.
* __Added bonus__: proper links and corresponding JS app logic to to work out what type of activity you were last looking at you're on.
* On this note we have not done the same with pagination as, for the user, we are still unclear as to whether this would be useful.

![page](https://cloud.githubusercontent.com/assets/31692/3360544/fb208f4e-faf3-11e3-8cc7-a6f0682acd09.png)
Maybe pull this url out in the a `var` - its a little opaque here.