Added pptx export support for bullet color.

Change-Id: I69306c8b3ace359f8dc243b83f89cfb570b9b73b
Reviewed-on: https://gerrit.libreoffice.org/14966Tested-by: David Tardon <dtardon@redhat.com>
Reviewed-by: David Tardon <dtardon@redhat.com>