what3words validation limited api

[amakunin]

what3words API allows for 1000 conversions w3w to coordinate per month https://developer.what3words.com/public-api.

We can make sure we store the coordinates table for the previous searches and use the API only for new locations. Similar logic was applied to OSM API - whole objects were stored in that case.

Also, need to set up API key to get access properly.