[WIP] Twig integration

This pull request is a try to improve the builder by using twig.

**Plan**
- more readable code
- decouple data and views

Future steps could be to improve handling of behaviours.

**Current state:**
*Code*:
Currently I replaced some single methods in the `ObjectBuilder` and the `ExtensionObjectBuilder` with twig templates, but maybe later we can replace the complete `build`-process with rendering the templates.
Also some protected methods were required to become public because the templates need to access them, I need to find a solution for this.

*References:*
#182