Explore grouping options for visually grouped checkboxes

[terracoda]

Sims like Projectile Data Lab have many interactive controls and thus many Tab Stops (16 Tabs stops in the Play Area) making efficient and intuitive navigation with Alternative Input challenging to design (see comment phetsims/projectile-data-lab#107 (comment)).

It would be nice to explore the possibility of a group option for sims with many controls. A group of checkboxes that are visually grouped could then be navigated with the arrow keys similar to other group controls work (e.g., list of radio buttons in a radiogroup).

As an example, Projectile Data Lab has five checkbox controls that are visually grouped into 2 separate grey boxes.

If we had a group option, we could create two groups for Alternative Input in order to turn 5 Tab Stops into 2 Tab Stops. The individual checkboxes would then be navigated to using arrow keys like typical group navigation and toggled to checked/unchecked state in the same standard way (pressing the Space key).