Administrative boundary tagging on closed ways

[imagico]

I was inspecting the changes in rendering due to fixing #59 a bit further and wonder if we correctly interpret boundary tags on closed ways. I am in particular thinking about cases like

http://www.openstreetmap.org/way/162691988

and

http://www.openstreetmap.org/way/10364857

We interpret these as administrative unit areas (see the labels) and not just as administrative boundary lines although the mapper clearly intended the administrative boundary tagging to apply to the line and the name tag only to the place=island - and as i interpret them tagging conventions say that administrative units have to be boundary relations and ways with boundary tags are always just boundary lines.

I know this kind of tagging is inherently ambiguous and should probably be avoided (by creating a multipolygon relation for the island) but IMO ideally we should require administrative unit areas to be boundary relations.