Add lake elevation to rendering

[Gazer75]

Someone on the Norwegian section of the community forums pointed out that there is no display of lake elevation in the map.
Maybe this could be added. Showing the ele=* value, and in case of reservoirs also use ele:min=* to display the max - min elevations.
This is done on all official maps in Norway actually.

Example:
https://www.norgeskart.no/#!?project=norgeskart&layers=1004&zoom=10&lat=6750240.06&lon=76215.39

This map render also displays reservoirs with a different shade of blue to indicate its a regulated lake which can pose dangers. Especially in winter where the ice could crack as the lake elevation drops due to the hydro power plant using its reserves.
I'd love to see this rendered as well, but guess it might be special case for northern parts of the world where lakes freeze over.

[imagico]

About 4.6 percent of natural=water features have an ele tag. But probably a huge percentage of that are from imports.

For differentiating water area rendering by waterbody type see #3895, #3896, #4128.

[Gazer75]

I'm guessing the lack of tagging is due to no maps actually showing this information. People don't generally map things that never show up. And you get cases were people in frustration do silly things like adding a place node with the elevation in the name to get it displayed.