If a place node is already linked against a boundary, it should not
be used for linking again. It is usually a sign of a mapping error,
when there are multiple boundary candidates. This change just avoids
inconsistent data in the database, it does not guarantee that the
linking is against the more correct boundary.
When using a linked place as centroid for a boundary, check
first that it is really within the area. If it is outside,
just keep the computed centroid because a centroid outside the
area just causes havok.
Fixes#1352.
If a boundary relation has no label member preferably
link against a place node with the same place type.
Also inherit the rank_address from the place node (only
has an effect when linking via lable member or place type).
