Geospatial Search

Add Geospatial Search example to the FTS pages,
as added to Node.js SDK:
https://docs-staging.couchbase.com/nodejs-sdk/2.6/full-text-searching-with-sdk.html#geospatial-queries
.
NOTE check for each SDK whether `geoDistanceQuery` has lat,lon reversed, as implemented by
http://src.couchbase.org/source/xref/6.0.0/godeps/src/github.com/couchbase/gocb/cbft/query.go#573-580
and hence needs noting in the comments and with a callout, as per the Node.js example.