Reset dublincore metadata when a document is copied

Currently the copied document keeps the same author, creation date and last modification date as the original document. We should at least reset these metadata with the current user as the new author and the current date as the new creation date and last modification date.

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Metadata dc:creator, dc:creationDate, dc:modification and dc:contributors are now reseted for documents created from a template (workspace template). You can also enable this behaviour fo all kind of document copies by setting nuxeo.dclistner.reset-creator-on-copy configuration property to true.