GroundTruth Refactor

[BryonLewis]

resolves #418

• May be a slight performance penalty but I think it's better to have non-groundtruth provide a direct link to the ground truth so it can be used to toggle on/off.
• The linked groundtruth will be the matching region with ground_truth=True with the newest date.
• The ground truth is not shown by default and instead in RDWatch it will link to ground truth when you turn it on using the Layer buttons.
• The groundtruth and model for the layer selections will enable/disable automatically based on the selected model. So groundtruth is inherently connected to the model-run instead of having to be toggled automatically.
• Updated the scoring response to label ground-truth vs the regular items respectively in the list.
• Updated the regular RDWatch response to label groundtruth vs the regular items as well.

RDWatchGroundTruth_small.mp4

[mvandenburgh]

Just left some code suggestions. Otherwise LGTM