Added snippet pagination

__Tasks:__

- [x] test coverage
- [ ] gather feedback for my changes

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | none
| BC Breaks     | none
| Doc           | none
Actually all of the above things could be abstracted away by our `ListRestHelper`: https://github.com/sulu-cmf/sulu/blob/b40ddca685e0e53a5d95b00f6dcf1826c41c8ac7/src/Sulu/Component/Rest/ListBuilder/ListRestHelper.php

I know we said we will convert to the field descriptors later, but using this class it would be less work then.