Right now sometimes it's lat, lon and other times it's lon, lat which
is just asking for horrors of biblical proportions.
I went through and carefully fixed them to take lat, lon in all places
I could find, and renamed y -> lat and x -> lon. I also removed
unused code, or code only called from tests: I think Lucene shouldn't
just export spatial APIs unless we also ourselves need them for
indexing and searching. Finally, I tried to shrink wrap the APIs,
making previously public apis private if nobody external invoked them.