Visualization of scalar parameters (advanced controls)

[denised]

Issue #332 asks for the ability to graphically look at different interpolation options for adoptions. In a similar vein, we could have a better interface for picking scalar values that makes much more use of the VMA backing data. I have mocked up an idea of what such a thing might look like at https://denised.github.io/mockup.

Note this really wouldn't belong in the solutions repo --- but including it here for discussion.