An artifact without the title annoation just gets the digest as name
which is less than ideal. While it is a decent default to avoid
conflicts users would like to configure the name.
With the name=abc option we will call the file abc in case of a signle
artifact and otherwise we use abc-x where x is the layer index starting
at 0 to avoid conflicts.
Signed-off-by: Paul Holzinger <pholzing@redhat.com>