Allow to set the image smoothing

[ivmartel]

The view layer sets the context imageSmoothingEnabled flag to false. This must become a settable class variable so that users can set it to true if needed.

[ivmartel]

Now, the question is what smoothing is used in what environment since the standard does not impose algorithms:

Bilinear scaling is an example of a relatively fast, lower-quality image-smoothing algorithm. Bicubic or Lanczos scaling are examples of image-smoothing algorithms that produce higher-quality output. This specification does not mandate that specific interpolation algorithms be used.

See canvas.html#2dcontext

And the answer is not easy to find... For now, I just found for chromium some info on SO, with link to this issue which would suggest that high quality could use bicubic interpolation, but it can change...