Support TLS authentication with provided certificates

[lfrancke]

This is the same as we did for ZooKeeper in stackabletech/zookeeper-operator#466

Client to Server is the most important one. I'm not sure if server to server communication can also be authenticated this way. I consider it optional.

This is done when

• the communication between clients and servers can be authenticated using TLS certificates
• the foundations (e.g. AuthenticationClass etc.) are used (from the ZK ticket)
• documentation has been added
• integration test has been added
• example has been added
• feature tracker has been updated (@lfrancke can do this if needed, ping him)

[lfrancke]

@soenkeliebau Could you take a quick look at this ticket and see if it is sensible and if not add/edit appropriately?