fdo#49678: ODF export: add svg:viewBox to draw:connector
fdo#49678: ODF export: add svg:viewBox to draw:connector

This attribute is mandatory; for the given bugdoc various
svg:viewBox="0 0 2500 1" are now written.

Change-Id: I7ea2294e0796546dcbb245993c01c2dd2b2a755a

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core