Implement improved info buttons [#58617804]

Expected behaviour:

- With JavaScript: 'more info' link activated on click
- Without JavaScript: 'more info' link activated on hover

Tested:

- Chrome, Firefox, Safari, with and without JavaScript
- IE6 to IE9 with JavaScript. Unable to test IE without JavaScript as GOV.UK is totally broken in IE with no JS, reported to Mainstream

Finishes [#58617804].