Translate german strings, potentially user-visible - sw/source/filter/ww1

These are mostly assertion-like messages.

Change-Id: Iabf8e2ea3411c51756765e160a9e654b06ca005d
Reviewed-on: https://gerrit.libreoffice.org/8356
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>