Investigate better UI from single time step -> two time steps -> more than two time steps

[nikmolnar]

From @brendan-ward:

I know we discussed this at length, but I'm finding the interaction somewhat unintuitive:

1. select species - it shows up in green. (great!)
2. select a future projection - new colors red and blue show up, which will make a whole lot more sense once we have a legend.
3. turn on an additional timestep - new colors go away and now there is much less green. Wait - what??

I think the problem is that we are really allowing 2 separate routes through the same UI elements:

• compare 2 timesteps and show: gained, same, loss
• compare multiple timesteps and show only the pixels that stay the same under all.

Should we approach these 2 routes differently from a workflow perspective? If we did so, we could make the UI and associated changes on the map more intuitive. E.g., if I am comparing 2 timesteps, then the futures should be presented as radio buttons or even a dropdown (probably better): I can only pick one future to compare to, and then it is really clear that I can look at gain, same, loss

Then if I want to see what remains the same under multiple timesteps, I can choose that route, and choose all the timesteps that I want to intersect together.