Ovito 3.11 Updates required

[mariaward10]

Tried to use the Diffraction Pattern Overlay in Ovito and got the following error:

Traceback (most recent call last):
File "", line 26, in render
RuntimeError: The viewport field has been removed from this deprecated class in OVITO 3.11. Please use the modern ViewportOverlayInterface instead to implement your custom viewport overlay.

[joaander]

@janbridley made some updates related to this in #30.

[mariaward10]

Thank you!