Fix copying lang files under windows, again
The descartInstances in AbstractDescartHandler is now a map

Each descartes instance now corresponds to the div, which holds the canvas. So, each instance of descartes now gets mapped to a canvas.
Add Simulation canvas
DescartesHandler may draw just a given array of divs
WebView.drawPlot draws the plots of the currently open tab
Merge branch 'library' of https://github.com/OpenACCEL/OpenACCEL into library