[Tagging] natural=bay on areas

[Juan Pablo Tolosa Sanzana]

> I didn't know about the practice of mapping the coastline along the baseline, AFAIK we don't map the baseline, only their 12nm offset (maritime borders)


Vice versa, the practice is mapping the baseline along the coastline. 
But I think this is no a good idea, because baseline extend up a bit 
outside of the coastline, if the baseline runs along the low tide. In 
some places the tidal range is huge.

The example of  Rio de la Plata exposed previously is clearly poorly 
mapped according the definition of natural=coastline. Note that 
according IHO Rio de la Plata is a sea.