Provide documentation about how to configure TLS for the client and server side

**Issue by [jrudolph](https://github.com/jrudolph)**
_Tuesday Feb 10, 2015 at 15:39 GMT_
_Originally opened as https://github.com/akka/akka/issues/16829_

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In spray we had only very sparse documentation about this topic and referred to the general SSL configuration of Java. It may make sense to provide proper documentation about this topic or at least provide working examples showing how to configure SSL in the most common situations.
- configure server certificates
- configure certain ciphers on the server and client side
- add a custom CA certificate to the client side
- disable certificate checking for testing purposes

/cc @sirthias

Also see spray/spray#721.

No file or test is named in the issue. Start by locating the existing Akka HTTP TLS/SSL documentation and its references to Java SSL configuration, then check how the four requested cases are currently covered. Done means clear, working examples for server certificates, cipher selection, custom client CA certificates, and disabling certificate checking for tests.

Written by the indexing model from the issue text.