`sino_normalization` add url handling

for now preproc/sino_normalization can be either empty or set to Chebychev. It would be nice if it can also handle an array.

Either by having directly the DataUrl:

sino_normalization = silx:///data/data.h5?/data/dataset

Or using another entry

sino_normalizationsino_normalization = dataset
sino_normalization_url = silx:///data/data.h5?/data/dataset

The dataset target can be 0D, 1D or 2D (not sure 3D is useful ???)

Then this should apply a subtraction to the sinogram