scans-provider: Added lut/norm/autoscale to the API

This MR provides a lut/norm/autoscale to the scans provider image API.

Without that, most of the images will not be displayed properly (pixels are saturated) if reached as an image.

This using math API from silx to speed up normalization and the use of LUT.

@tvincent on side note, i did copy a huge part of the private silx API to avoid Qt/matplotlib import. This could be moved to another place in silx (for the next version) if you think it's fine, like silx.image, else it's not a huge problem.