Fetch mapit boundary data on search page

Assigns an `@authorities` hash to the view with `DIS` and `CTY` boundaries - or a `UTA` boundary in the case of a Unitary authority (e.g. Southampton - `SO14 OAB`).

Includes an `NPA` boundary if also covered by the South Downs or New Forest National Parks Authorities (e.g. `SO21 1PL`, `SO42 7QH`)

Passes the original query through to the search results page as an address or a postcode param
Unless this breaks something by it's presence, it's probably not necessary to remove this, it's only returned by mapit vhosts in staging/dev mode (hence why you're seeing it at the moment) and will be gone in production.