[jupyter] add support for RCanvas
[jupyter] add support for RCanvas

Set special "jupyter" kind of web display
Detect if RCanvas compiled
Like with RCanvas, extract list of RCanvas after each cell
Use RCanvas methods to create JSON and then display it

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root