Dark/white data are lost for internal pipeline operators

[psavery]

If you have a data source with dark and white data, and you run an operator on it in the internal pipeline, the dark/white data are lost in the process, and the child data does not have dark/white data.

If we want to support this, we will probably need to perform some of the operators on the dark/white data too, so that they retain dimensions matching the original data. For instance, for a bin tilt images 2x, we will need to bin the dark/white data as well.