Support running logical replication locally for easier development

[jrafanie]

• Document existing way to test logical replication with migrations using multiple appliances
• Subscriber? was always true for intracluster replication, so use publisher? first to better identify the replication type
• Enhance subscriber? to fix prior issue by allowing an optional database name to be provided so only subscriptions for the optional database would count for a true or false result. If not provided, the default behavior is kept.
• Add create replication slot method
• Change manageiq code to use new pg-logical_replication release and utilize create_replication_slot method to support intracluster replication by creating the slot and subscription separately.
• Create basic rake task/documentation to setup a local replication environment for testing and development

[Fryguy]

Done!