CardPanels are not Screen Reader ACcessible

Just breaking down one of the issues from #5920 into something hopefully a little easier to do a PR for :)

Cards are not currently accessible for screen reader users. The information on cards is available, but screen readers cannot currently focus on cars, nor read information from them. This makes it almost impossible to play the game as it currently stands.

Resolution:
Card panels should be exposed to screen readers using the Java accessibility API. Ideally they should expose information about status (tapped, flipped, etc.) as well as name and other card information so the screen reader doesn't have to access this information in multiple places.

The [AccessibleDescription](https://docs.oracle.com/javase/7/docs/api/javax/accessibility/AccessibleContext.html#accessibleDescription) seems like a good place to put information about card status and other things, though other implementations are probably possible.

Ideally this should work regardless of the display mode or other settings a user might happen to enable.