Killing the subprocess after using the visualizer #87

I notice two issues with using meshcat to run my visualizations for simulations developed on pinocchio:

1. I cannot effectively kill a meshcat visualizer completely, and thus, its server. Vizualizer().delete() just deletes the path and Visualizer().close() fails since ViewerWindow().close() has not been implemented. This would not be a problem if issue 2 below is addressed.

2. I use Meshcat visualizer by calling Visualizer(zmq_url=None, window=None). When I do so, the ViewerWindow() internally creates a zmq_url, zmq_socket and a subprocess. Once I am done using the visualizer, I would like to delete it, end the program, start a new program and create a new visualizer. But by doing this, I am assigned a new URL and subprocess every time, resulting in a pile up in my system's processes. I see that this is because the subprocess is not killed when I end the program or delete the visualizer. It would be ideal if killing the subprocess and closing the socket could be handled by Meshcat or by calling a Meshcat method such as Visualizer().close()