modernize views3/plot.html, move to mvc/, add scatter to Plot.js

This is an early demo that used Chart.js and without latest C's in MVC.
Change to: 
Use GUI.js, Plot.js & use Animator, add Mouse
Move to mvc/
Will be a good test of can uPlot be used rather than sexier Chart.js.
We'll need to add scatter plot to Plot.js. Can uPlot do this?