Add model fit and lower/upper bound options to Scatterplot from XY graphs

DavidChurchman

Adding a model fit and lower/upper bound to scatterplots would be very helpful.

Here's what's available in XY graphs:

And here's a use case for a scatterplot, which I think is actually more common in the real world than what Domo implements for line graphs:

A runner-up option that would be helpful is symmetry shading, or being able to define shaded regions with a line that isn't horizontal/vertical: