Added barman support and modified postgres service to better fit to puppet way

I have added a parameter barman_server. If you set this to a fqdn of a barman server, then puppet will add that is required for barman support in the replicated cluster setup.
Furthermore, the ssh module is split in two and the sshkey part is moved to the pure_postgres module.
The ssh key part must be called with a list of ssh keys that should be added to the known hosts of the server
Last but not least, the service part is modified to better fit the puppet way of resource management.

• All the service stuff is moved to the pure_postgres::service module (to fit to proper module layout)
• A init parameter sets if the service should be managed by the module or not.
  • Managed: pure_postgres starts the service
  • Unmanaged: pure_postgres::start can be notified, but will not be started by default
• pure_postgres::started is now a definition. Both pure_postgres::start and pure_postgres::restart use it to check that postgres is up after class is finished
• pure_postgres::reload and pure_postgres::restart are refreshonly
• pure_postgres::service now rather initializes the services that taking action
• This new setu better fits into pure_repmgr::config. Required changed are applied as needed.