Instrument the play area panels

[samreid]

For #38, we would like to be able to hide the entire slider control Panel, not just the contents of the panel, and we would like the content tandem to be nested in the panel tandem. I'll demonstrate one way to accomplish this for the Energy screen.

[samreid]

Please see the hookes-law commit for how this was accomplished. @pixelzoom can you please review and, if it seems good, apply the same strategy to the other screens?

[pixelzoom]

Looks good. I applied the same pattern to the other panels. I shortened tandem name (e.g.) "springConstantControlPanel" to "springConstantPanel" throughout. @samreid Take a peek, close if this looks OK.

[samreid]

The change sets look great, closing.