tdf#75256 Sifr - Adding new fillcolor icon and modified insertbookmark

I took the insertbookmark icon from the gnome symbolic set and tweaked it
a bit and it is now flat instead of pseudo 3d.

Reviewed-on: https://gerrit.libreoffice.org/16717Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
Tested-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
(cherry picked from commit 8b788891)

Change-Id: Id29f3c15515def2f461d8ea45aca427594f290bc
Reviewed-on: https://gerrit.libreoffice.org/16737Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>
Tested-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>