Fix JSF Web UI view/delete of placeless doc

Placeless documents (like stored renditions) shouldn't crash the JSF web UI. At least the following cases must be treated:

• putting in trash through trash service
• UI redirection after delete
• URL generation

When putting in trash, as there is no natural "trash container" from which to un-trash, we'll do an immediate delete.

For URL generation an id-based pattern must be used, as a path doesn't make sense.
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Placeless documents like persited renditions can now be browsed in the JSF UI without any crash.