Fix failing test, probably fix real live problems with renaming dx objects

the bulk of the test fix happened in plone.app.referenceablebehavior
Last skipped test unskipped

Unfortunately there seem to be slight differences
between rich text rendering of AT and DX.

As before, most changes were necessary in
referenceablebehavior.

@saily \o/
Documenting @@updateLinkIntegrityInformation

Two line note about the existence of @@updateLinkIntegrityInformation view
Reaplied on correct branch.

Revert "Revert "Update tag for id=content element to article instead of a simple div.""

This reverts commit 9946cee80d8eb33005c0774694e6fd86d3f3ea60.