Hide banner_notification conditionally on homepage

Whenever we hide the navigation, we should also hide the banner
notification.

Fixes #433.
Merge pull request #432 from alphagov/bugfix-campaign-header-bar

Move banner_notification into after_header block
Removing the location icon from postcode forms

example - https://www.gov.uk/recycling-collections

This layout is broken on mobile and after discussing with designers
it was agreed that this icon is superfluous. So I've removed it
and the images.

https://www.pivotaltracker.com/story/show/73192808