Remove lists

Back at the beginning of this project, I used lists for these checkboxes because it was thought that organisations would want nested checkboxes within other checkboxes. This has not happened, so I am removing the functionality to have nesting.

First step is removing the lists and replacing the ul with a div, as some of the height calculations that the javascript is doing needs an inner element to the checkbox container.
Rip out unused features

Now I've removed the ul/lis from the select facet view, we can remove the support for nested checkboxes from the JavaScript and related tests. Woohoo!
Rename js-inner to js-auto-height-inner

js-inner is not a very good name. Since we're using this div for height calculations only use js-auto-height-inner instead, which is more meaningful.
Merge pull request #127 from alphagov/remove-nesting

Remove nesting