tidy metadata and crumbtrail css

- increase contrast between metadata/crumbtrail and description
- makes metadata styles consistant between two tabs
remove topic and document series from metadata

the metadata was just getting too long to be useful
Update gds-api-adapters to 6.1.0

There was some significant refactoring in the gem. I need some features that
are about to be added, so this is a step to be able to upgrade to that.
Basic presentation of organisation search filter

Not wired up to get real data, nor does the filter have any effect.
Organisation filter retains tab param on submit
Retain the organisation selection on filter
Pass the organisation filter to Rummager
Fetch the organisations list from Rummager
Constrain the width of the organisation dropdown

Some of the organisations have very long names. Technique approved by
@tombaromba
Sort organisations in the filter
Retain organisation filter on a new search
Always show all search tabs

If you run a search that returns no Government results, or no government
results with the current organisation filter, the tab would be hidden.

This is problematic for several reasons:
* if you were filtering down results in the government tab, it's suddenly
  disappeared. If you want to change the organisation filter, you can't.
* it appears that there are no results, even though there may be, if there was
  no organisation set. You can't see that you're filtering to an organisation,
  nor which organisation it is.
Hide the organisation filter behind a feature flag

We need to play with the UX and design, and user test it before we're confident
enough to turn it on by default.
Merge pull request #345 from alphagov/meta-data-tidy

Meta data tidy
deleted search results numbers and changed tab description
changes to test for shouty tabs
Merge pull request #347 from alphagov/remove-tab-numbers

Remove tab numbers
Make tests for top result handle 3 results
Bring the first 3 results to the top
Overhaul the tab selection logic

Since all tabs were enabled if there were any results (in https://github.com/alphagov/frontend/commit/98e46d50b52a80ffb4c77d6b568c6b9d318af41d )
the behaviour of tab selection has been suboptimal. If you had specified a tab,
it would be selected. However if you hadn't, it would default to the first tab,
even if that was empty and another tab had results.

The active tab is now decided in this order:
  1. user-selected tab (supplied in the ``tab`` querystring parameter)
  2. the first tab with results
  3. the first tab