Styling: sources -> bounds is not reflected in the editor

[prusswan]

Description of the bug:

Under the style specification, raster/vector sources can have an optional bounds parameter. However, this value is not shown in the editor (hence it cannot be verified or modified in maputnik). This may cause confusion to users who are unaware of this issue.

Steps to reproduce the behavior:

1. Create or import a style with a data source that has bounds specified
2. Observe that the style is applied in the map, but not fully shown in the editor (i.e. the bounds value is not shown).

Style file or style URL (partial):

  "sources": {
    "source": {
      "type": "vector",
      "minzoom": 0,
      "maxzoom": 17,
      "bounds": [140,20,150,30]
    }
  }