Add tests for multi-polygon diff import issues reported in trac #2853

When using old-style multi-polygon tagging with both outer and inner ways
tagged with the same tags, then if the tags on the outer ways change,
osm2pgsql should create a new inner polygon to be consistent with fresh
imports.

This is currently not the case, so osm2pgsql doesn't pass these tests. They
are for now therefore disabled
Another attempt at improving the copying of multi-polygon tags from outer ways

Only copy over tags that are present on all outer ways to the relation.

Member ways need to have all their tags on the relation, otherwise they will
be processed independently as ways.

This is in response to issue #80
Fix summery statistics in test after the change of stylesheet caused the tests to fail