Update the structure of metadata on document pages

Move from lots of desecrate bits of metadata to a more unified approach
with only a 'part of' or 'from' metadata.

Remove the old document_metadata method in favour of two helpers one for
part of and one for from. They both return an array of links which can
then be output in either the top or bottom of the page.

Updated the tests to ensure all the items which should be outputted for
each method is.

Moved the operational_field and location metadata items to the extra
metadata partial. They don't make sense in either part of or from and
are only used by one format.

Added classes on to each type of link which is going to be displayed so
we can continue to get analytical data for them.
Refactor hide extra rows

Hide extra rows didn't work so well with inline content and only really
worked with block level children. This updates hide-extra-rows to be
able to hide inline content like that found in the metadata on a
document. It adds a call to it on the new document metadata.
Use locales for new metadata

Also update all the locale files to match this change.
Update metadata link tracking for new style

Update the link tracking for the new format metadata links. Now uses
different logic for the top and the bottom because the mark up is to
different to use the same.
Localise the footer metadata headings
Move assignment into condition
Use non-exact matches rather than regex

Using interpolation in a regex doesn't escape the string being
interpolated. This could cause some unexpected results. Use a non-exact
match instead.
Merge pull request #1519 from alphagov/change-metadata-structure

Change metadata structure and display 

https://www.pivotaltracker.com/story/show/70352364