Added Template var to resolver (Twig-Template)

__Tasks:__

- [x] test coverage
- [x] gather feedback for my changes
- [x] submit changes to the documentation

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | #510 
| BC Breaks     | none
| Doc           | (fixes bug in the doc)