This should make it easy to reuse the mapping code wherever
necessary and restores the loading of writerperfect documents.

Change-Id: I505bffa47fe37270b0430d9ae5afec5072762b4c
Reviewed-on: https://gerrit.libreoffice.org/35263Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: David Tardon <dtardon@redhat.com>