Add small icons for conditional formatting to galaxy so they show in tango

Change-Id: Id8b7615610b7eb190c64b88a157df7a498b9cd09
Reviewed-on: https://gerrit.libreoffice.org/12959
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>