EZP-23317 Twig Helper to get field Definition name in a template

Closes #980 

Todo:
- [x] Improve the code in terms of CS, optimization and allow use of Content + VersionInfo
- [ ] Add generic helpers for ->names and ->descriptions (3fd0b86) / incl support for existing functions: getName() and getDescription() 
- [ ] Unit tests
There should be an `array_unique()` on `$languages` as you may have the main language twice.