Rarefaction processing upgrade

[Patg13]

The idea here would be to allow using a list of rarefaction level instead of a single one, that would save steps if multiple rarefaction level must be used instead of a single one.

It would also be possible to automatically infer a rarefaction level list from the filtered table and the rarefaction curve, but it would require some development (especially for the rarefaction curve interpretation, maybe use tangent between two points and keep level when the resulting X in the mX+b formula is the close to 0)