SvDataCopyStream used to do extra Load/Save things that are long
gone, so there is no reason for the common base anymore

Change-Id: Ib321021002adb480bb96298f199141dc3fe2ec2b
Reviewed-on: https://gerrit.libreoffice.org/32851Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>