Improved and fixed twig reference

| Q   | A
| --- | ---
| Doc fix? | yes
| New docs? | yes
| Applies to | 2.3+
| Ficket tickets | #4301 

Removed the ugly looking tables and added some more details.
What do you think about ``_reference-twig-function-render`` instead? We use dashes instead of underscores or dots for labels most of the time.