Improve the whitelist view

- Add the ability to filter the whitelist table, like the organisations table.
- Add a Cucumber spec to test that only admins can access the whitelist.
- Highlight the row containing the domain just added, so it can be found easily and we can spot typos.
- Add the ability to sort the table by date added, in either ASC or DESC order, using the TableSorter jQuery plugin.

(Rebased today (17th June) against master.)
Let's not use it then - the comment covers it and if it exists it makes people ask "what's the hook there for? Something must use it, but it looks odd on that `script`"

It'll be moot when you've paired with @fofr anyway - this'll go away in favour of a module class placed on other markup.