Add a Location Chooser to streamline query construction

[riordan]

Just like we bake the location of the api key into the query, we should also be able to do the same for a location (e.g. a city).

This can either be from a pre-baked list or the autocomplete coarse geocoder (when we make it [pelias/api#337]).

Ideal Features:

• Easy to toggle on / off
• Ability to activate location elements for each query type
  • e.g. search:
  • focus.point - centroid
  • focus.viewport - bbox

[mariusbobo]

As a quick step forward, can this be just 2 form fields, lat/long, which default to current browser Geolocation API, and have these passed to URL and used in tests?