Bump gds-api-adapters to 7.2.0

This picks up the new fact-cave end point.
Add an initialiser for the fact_cave
Wrap our govspeak interpolation in a presenter

This will keep all of the logic that involves facts in a single place,
rather than being mixed between node_ and smartanswer_ presenters.
Hook up the GovspeakPresenter to the NodePresenter

Enables a given node to have interpolated facts.
Integration test for SmartAnswer node fact interpolation
Use `unless` instead of if negate
i18n setup/teardown is no longer required for these tests
Render the HTML before interpolating facts

This is just in case a fact in the fact cave happens to look like
markdown or use one of our special govspeak characters.
Merge remote-tracking branch 'origin/use-facts-in-markdown'