Add geocoded search and postcode search to the homepage

* Restores all original routing
* Restores original javascript files in the code assets directory
* Creates `hampshire.` namespaced  javascript files (to avoid name clashes) in the theme assets directory
* Overrides the `address` and `search` actions of the applications controller
* Themed views for:
 * `shared/_end_matter` - to use `hampshire.application.js` instead of `application.js`
 * `applications/address` - custom homepage
 * `applications/search`
* New spec file to test that the theme works
* New `MAPIT_URL` setting in `general.yml`

Closes #1
Closes #2
It would be good to have a few more tests here along the lines of:
- submitting good data and getting the response we expect
- submitting a valid-looking but non-existant postcode
- submitting an invalid postcode
- a not-found address