Add SSL support in RabbitMQ

[vincent-zurczak]

RabbitMQ allows secured exchanges between the server and clients. Roboconf should support such secured connections and update the messaging configuration in consequence.

Obviously, SSL support will only be another option in the messaging. The current mode (user/pwd authentication) will keep on being supported.

[vincent-zurczak]

As a reminder:

• https://www.rabbitmq.com/ssl.html
• http://roboconf.net/en/user-guide/security-and-https-console.html

[vincent-zurczak]

The specifications were written. See http://roboconf.net/en/user-guide-snapshot/security-rabbitmq-over-ssl.html

Postponed to version 0.9.

[vincent-zurczak]

Real messaging tests (unit and integration tests involving a real messaging server) are disabled by default. They have to be run manually in association with https://github.com/roboconf/rabbitmq-with-ssl-in-docker