Extract service form fields into partial

To reduce duplication between new and edit views
Add location_match_type to Service model.

To indicate how places for a given service should be matched.
Add snac field to Place model.

The local_authority lookup type will match on this.
Move location lookup logic out of controller

This will make it easier to test and to add the lookup by local
authority functionality
Add MapitApi method to fetch snac for a postcode
Return places in district for local_authority services