The logo directory wasn't really referenced from anywhere. Additionally
there wasn't any reasonable index for all the image files which we have.

Turn the README file into rST and display the images it references. Link
to the new index file from the docs page.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>