Feature: ability to specify dataField in GeoDistance components

**Issue Type:**

Enhancement

**Platform:**

Web / ReactiveMaps

**Description:**

Currently, the GeoDistance (Dropdown and Slider) components work by using Google's location search functionality, and then fire a query against the selected distance range.

This issue suggests that if a user already has location data in their ES index, we should allow them to optionally search against it (v/s strictly using Google location search).

This can be done by the use of `dataField` - when a user specifies the data field, they declare an intent of using this field to search the location data against (and use the ES index). When they don't specify this, Google's location search will be used against.

We can also take the location field ( (lat,lon) points) via `locationField` (currently, this is specified by dataField), which will eventually be used for firing the GeoQuery.