Hide features that require AKA domains if none

This will help user experience a little, and be an additional prompt for them
to get AKA domains set up.

It doesn't help people who have been given a link to the side by side browser
directly.
Merge pull request #244 from alphagov/hide_features_that_require_aka_domains_if_no_aka_domains

Hide features that require AKA domains if none