core+setup: adding the public glance repository

This patch adds a stored procedure to add the public glance repository,
and in addition a setup plugin that uses it, if needed.

Change-Id: I415dd452f644e1adf150713f3dfdc094ae9af160
Bug-Url: https://bugzilla.redhat.com/1053544
Signed-off-by: Oved Ourfali <oourfali@redhat.com>
(cherry picked from commit 146b9c89e8cc4ddfd05fb038cdaf6d6c126e2845)