Passing RequestAnalyzer to UserRepository

Moved the part which gets the security system to the UserRepository

__Tasks:__

- [x] test coverage
- [x] gather feedback for my changes

__Informations:__

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| Tests pass?   | no => https://github.com/sulu-cmf/sulu/pull/101/files
| Fixed tickets | none
| Doc           | none