Grouping fields

We need a way in our config to group fields.
Aside of the simple group entity we also need to define the type of the group.This means that we can group fields inside a component like [Tab/Menu](https://semantic-org.github.io/collections/menu), [Accordion](https://semantic-org.github.io/modules/accordion) or [Step](https://semantic-org.github.io/elements/step) 