a) factor out part of SvXMLEmbeddedObjectHelper::ImplGetStorageNames as
splitObjectURL to reuse in SvXMLGraphicHelper::ImplGetStreamNames to get better
url splitting logic to handle "./ObjectReplacements/foo"

b) FN_UNO_REPLACEMENT_GRAPHIC_URL and FN_UNO_GRAPHIC ids collide
urls incorrectly treated as graphics

c) imported preview images for objects set on a temporary
svt::EmbeddedObjectRef *copy* of the object, not the real object.