[Tagging] Adopt-a-highway representation in OSM (this time in plain text)

[dies38061 at mypacks.net]

There is a thread of discussion on the Talk-us board about how and whether to represent Adopt-a-highway features.  See http://lists.openstreetmap.org/pipermail/talk-us/2013-January/010086.html as the top of the thread.  It was suggested that this come over to the tagging board for further discussion. --ceyockey