1034574: Alternate message based on why no repos exist in GUI

Alternate the no repos message based on why there are none.
Either there are no repos due to no entitlements, or
because there are no repos provided by the current
entitlement certs.
Merge pull request #833 from candlepin/mstead/alternate-no-repo-message

1034574: Alternate message based on why no repos exist in GUI