:microscope: Clean up parameter passing across generators

Rationale:

- Different generators handle their options differently. E.g.
  tabs_for doesn't have a "data" to generate tabs upon, while
  the others do

- All generators do parameter forwarding to the definition block,
  and forwarded parameters are everything after the required ones.
:neckbeard: Separate Field#content and #value, for more composability with other frameworks