Allow RubyPosition property to be set via UNO
interface.

Change-Id: I506312b1b5b27f016d0ee1c66231ff90747e5538
Reviewed-on: https://gerrit.libreoffice.org/48327Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mark Hung <marklh9@gmail.com>