fdo#85594 enable conditional formatting button, add icons, and tooltips

Change-Id: Ia6fa678fba21f48de183798bb33ee2e34598b03e
Reviewed-on: https://gerrit.libreoffice.org/13022
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>