Add a phet-io API call to get the order of the cards in the median screen

[samreid]

From #204

On the median screen:

Get card values in the order they appear (i.e. kick order) as an array

• client could get the order of the cards (which is in the order the balls were kicked rather than ordered on the number line)
• We will add an API call that the user can query on-demand.

[samreid]

@marlitas and I wondered if there should be a card container model. If we implement/refactor that, it would impact this issue.

[samreid]

After the commit, you can get the values of the cards like so: await phetioClient.invokeAsync('centerAndVariability.medianScreen.view.accordionBox.cardNodeContainer','getData',[]);. We will have to decide whether we want to move this to the model. And also tagging for #136

[marlitas]

@matthew-blackman and I reviewed the changes. We just made some small documentation adjustments, everything else looks good. Tested in studio!

[catherinecarter]

Updating the command to:
await phetioClient.invokeAsync('centerAndVariability.medianScreen.model.cardContainerModel','getData',[]);

[samreid]

New command: await phetioClient.invokeAsync('centerAndVariability.medianScreen.model.distanceAccordionBox.cardContainerModel','getData')