[Tagging] tagging single trees

[M∡rtin Koppenhoefer]

Many people are tagging single trees, and usually use natural=tree for
this. Now there are some voices on the German ML that say,
natural=tree is reserved for "special" trees, and can therefore not be
used for "ordinary" trees.

I changed the wiki according to what I perceive actual usage, by
changing "lone or significant" to "single". Unfortunately this is
disputed at least by a few people.

What are your opinions on that?

cheers,
Martin