Add demo comparing dQ/dt methods CTS, VTS, and ETS

[mgcooper]

Is your feature request related to a problem? Please describe.
The benefit of VTS and ETS is not currently communicated in any demos. This will also ensure that these methods do not produce errors as the toolbox is developed using ets as the default method.

Describe the solution you'd like
Add a demo as described. Show how the horizontal striping in the point cloud plot can be used to guide the choice of vtsparam. For the demo data, compare 1000, 10000, and 100000. See how the fit changes at 1e5.

Describe alternatives you've considered
Add a test.