Add a new property for the blur radius and define an ID
for it to support the import of OOX files. Add a test for
importing the blur radius from PPTX file
Change-Id: Iffaa33ff7159019ce9478cee558622bd61bcf60e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/95090
Tested-by: Tomaž Vajngerl <quikee@gmail.com>
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>