HSEARCH-1273 Adding tip about default spatial field name org.hibernate.s...

...earch.annotations.Spatial.COORDINATES_DEFAULT_FIELD.

Also reviewing and fine tuning rest of spatial chapter.
Ok admittedly the original sentence wasn't great, but the point is we should not persuade people to use this as a replacement for Hibernate Spatial, but rather the point should be that it's about combining the fulltext (name of the restaurant) while applying a distance based restribtion _as well_.
While you improved readability, it lost the core of the message about combining the two aspects.