Fix sea labels
This fixes a bug that caused sea labels to not actually be rendered if they were just label points rather than converted polygons.
The one zoom they worked properly at was z16 which was the only zoom we tested at. I changed to the test to check different zoom levels.
Generally LGTM, but screenshots or build details to verify please.
@jeffdefacto @peitili @travisgrigsby This should be ready to roll now :)
I see you expanded upon my PR a little bit haha @nvkelso
@jeffdefacto Thanks for the initial work here! It turned out to be a very meaty problem to dig into, and good way to keep busy now that I have more time on my hands ;)