I'm reading here that "section" and "group" are the same thing, but that `section` is being defined on the control, while `group` comes from the JSON hierarchy.

I definitely want to support adding controls to pre-existing sections (or even better, *move* pre-existing controls *into* new sections). I'm just hung up on what the data structure should be.

When seeking to extend sections, you might expect this to work:

```JSON
{
  "Colors": [
    { "selector": "#page", "type": "color", "label": "Adding to the color section" }
  ]
}
```

I think the only reason that *doesn't* work is because I'm intentionally prefixing Group ID's to *avoid* conflicts: [styles-helpers.php#17](https://github.com/stylesplugin/styles/blob/master/classes/styles-helpers.php#L17).

Maybe a different approach would be best: instead of auto-prefixing, strip a prefix from the `label` if it exists. I'm almost positive that if you remove the prefix from the line above, Group names will allow adding to existing sections.

This brings up another question, though: what about if a pre-existing section has a label that doesn't match the ID? It might not be an issue... But there might be other things that we'd want to modify about a section. What about a whole section metadata type?

```JSON
{
  "Colors": [
    { "type": "section-meta", "section_id": "default_colors", "unanticipated_section_wide_feature": "true" }
  ]
}
```

Thoughts?