Copy tweaks around searches after user testing

Publishers often got confused whether the searches displayed were the
searches that led to that page, or searches made *on* the page. The changed
wording seems to have cleared up the ambiguity somewhat
Replace user-facing quotes with smart quotes
Merge pull request #29 from alphagov/copy-tweaks

Copy tweaks
Increase cache expiry time to 12 hours

The underlying data for this page won't update more than every day so
we should set a better cache time to reduce the number of requests we
receive and make to our dependent services.
Merge pull request #30 from alphagov/increase-cache-time-to-12-hours

Increase cache expiry time to 12 hours