ICONS: add duplicate entries for object forward and backward in writer/calc

Change-Id: Ifa6aecea14f3e3ca0443c2de1690054f601addcb
Reviewed-on: https://gerrit.libreoffice.org/13502
Reviewed-by: Yousuf Philips <philipz85@hotmail.com>
Tested-by: Yousuf Philips <philipz85@hotmail.com>