Pass base urls to the API app
Pass base urls to the API app

This gives the API a simple way of knowing where the main application
is hosted and where the API is mounted within it. This is
used to generate links in the API output.

mysociety/popit,openstate/popit,Sinar/popit,mysociety/popit,mysociety/popit,Sinar/popit,openstate/popit,mysociety/popit,Sinar/popit,mysociety/popit,openstate/popit,openstate/popit,Sinar/popit