Whitehall search improvements

Dont use the `query_default` analyser by for the title match - this
causes issues where searches for 'passport' dont return anything but
'passpor' does

Implement the time decay from the main search and apply to all editions
for gain some form of date sorting, and change values (tails to boot of
1 and starts at 3.5) see graph:

http://www.wolframalpha.com/share/clip?f=d41d8cd98f00b204e9800998ecf8427
e1tsm9rnveh

Also move to the non deplicated `query_string` query type, we loose the
fuzziness control.

https://www.pivotaltracker.com/story/show/48726201
Fix stub in tests
Merge pull request #84 from alphagov/advanced-search-changes

Whitehall search improvements