Refactor functionality related to mapping results

- Replace `generate_map_data` method with client-side JS code

- Improve handling of markers with identical coordinates by shifting them by a random amount up to a configurable max distance (currently set to 50m)

- Define new @total_map_markers instance variable that can be used in the views to determine whether or not to display a map, and for the `format_map_summary` helper.

- Fix bug Ans introduced in April where the conditional for displaying `@map_search_summary_html` was removed. See the bug in action here: http://ohana-web-search-demo.herokuapp.com/organizations?utf8=%E2%9C%93&keyword=test+location+with+no+street