[Tagging] ele-key for lakes / water bodies and glaciers

[John Smith]

Since water levels, can fluctuate substantially both seasonally and
annually, I'm not sure of the benefit of the ele=* tag on bodies of
water, nor on contours since this is something you'd use DEM
information/files for.

*Maybe* I'd use them on glaciers, but only peaks, otherwise you just
end up polluting the DB with redundant information.