Implement PowerPointExport::WriteAnimateColorColor to export
to, from, by elements of the animClr element.

Change-Id: I0fb81f8838656c127610a9a10654e3e51106bea8
Reviewed-on: https://gerrit.libreoffice.org/57820
Tested-by: Jenkins
Reviewed-by: Mark Hung <marklh9@gmail.com>