New Batch form UI: Visual attack of the Config box

[kspurgin]

When I initially added the ability to optionally add a JSON batch config, I was trying to make it visually unobtrusive, since it's very optional.

Since adding the JSON validation stuff to it, the size and styling makes the Config box the most most prominent thing on the new batch form page.

Proposing the style be changed to something less heavy (maybe a grey background instead of that black).

Or leaving the style of the form box as-is, but hiding it unless you click to expand the Config section

[kspurgin]

@meganforbes - UI related improvement suggestion, if you have input/opinions