Wire up location search

Summary:
Location search will now select points within a 25km radius of the location.

Also
- Fix confusing demo-data point with invalid post_point entry
- Always clear map, even if geojson is empty

I'm considering this a first iteration. UI has some issues:
1. if there are no result the map won't move to show you where we geolocated you search to
2. After searching, if you zoom out the map will be missing points outside the search area, this could be confusing
3. No way to set the extent of our bounding box (hard coded 25km)
4. Ideally we should have autosuggest on the location search

Test Plan: - With standard demo data loaded, Search for 'Auckland'. Get  a couple of results

Reviewers: eyedol, shadowhand

Reviewed By: shadowhand

Maniphest Tasks: T120

Differential Revision: https://phabricator.ushahidi.com/D144