Add Ghost framework

We should add a framework to predict and subtract or flag ghosts. The model to determine where the ghosts are is yet unknown.

This is a mitigation strategy. That is, our baseline to deal with ghosts is to prevent observations that create ghosts. We should ensure that we have a framework to correct for the ghosts if the baseline strategy is not sufficient.

A ghosts-producing catalog of bright stars should be available, because we will also use that to prevent ghost-affected observations. So we can use that to predict the ghosts.

We should separate the 'predict / measure /estimate ghosts' step from the 'flag / subtract' step.