Add easy way to specify a place has no name

[gdabski]

Building on the idea from #752 , I suggest also introducing a button that could allow easily adding noname=yes (or name:signed=no) to a place. This is, like nohousenumber=yes in the other task, a tag that I end up adding manually through the tag editor, because otherwise people with StreetComplete come and add bull**** names that are in fact merely descriptions of the place.