F #58: Add support for custom / insecure repositories

[sk4zuzu]

• All repo code for [ceph, frr, grafana, opennebula, passenger] is now aggregated inside the repository role. This reduces maximal number of invocations of package cache updates.
• Repository role can be safely executed inside the 'all' inventory group as it auto-detects what repository types to install on specific hosts.
• GPG / SSL verification can be disabled per repository type. Together with custom urls it allows for arbitrary / insecure repos to be installed.
• Components like flow and gate conditionally call repository role now, so no preliminary / explicit repository call is required.