Remove format when creating link to next page

The format for the current params was set to json when ajaxing in
results. This was causing the next link to be to a json page rather than
the html page.
Remove infinite scroll

Analytics was saying that not many people ever got to the second page of
results with infinite scroll enabled. We were also reciving feedback
that people found it hard work not being able to use the back button
after scrolling down many pages of results.

This should remove infinite scroll but leave in the ability to ajax in
new pages of results.
Merge pull request #653 from alphagov/remove-infinte-scroll

Remove infinte scroll