Add es_score to documents

This is primarily for debugging scores
Reduce time boost and scope to announcements

Also increase minister boost as in some cases other documents score
higher - becuase of the title boost

Specify the search_format_types must be announcement
keep the score attribute name consistant
Update advanced search score test
More inside gov format tweaks
further boost organisations above other content
Merge pull request #62 from alphagov/whitehall-changes

Scope freshness boosts to the search_format_types announcement