[PATCH] Add freshwater fill tag to dump station preset

[brycenesbitt]

I'm resubmitting this one.

Most but not all RV dumps also offer a place to fill fresh water tanks, often
from the exact same coin operated machine. This patch adds water_point=yes/no
as such a tag, and moves the feature near the camping/RV section.

It is particularly important to know which stations are dry (water_point=no).

See https://josm.openstreetmap.de/changeset/8329/josm