Implemented SecurityListener

Enables the possibility to simply add an interface to a controller, add the `getSecurityContext`-method, and let then Sulu automatically check the permission.

Also added a public `getLocale`-method to the `SecurityInterface`, made this method public for the `RestController`, and adjusted other controllers when needed.

Do not merge before #563, because otherwise the system can't be configured to a useable setup.

__Tasks:__

- [x] test coverage
- [ ] gather feedback for my changes
- [x] submit changes to the documentation
- [x] add localization to check
- [x] remove unused privileges 
- [x] add entries to changelog

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | none
| BC Breaks     | existing installations have to configure the permissions correctly
| Doc           | https://github.com/sulu-cmf/docs/commit/60d277bf1a478aa151fe6c2201ad8eb069004812
again same answer :-P