Use custom resolution function calculator in workflow

The workflow code allows for easy calculation of convolved slices. It is good to take advantage of that mechanism. Currently the workflow is written to work with resolution function calculation process that involves mcvine simulation, fitting, and interpolation. However, we also want to be able to use an arbitrary resolution function generated in some other way. This is where customization comes in.

To do that, the main thing is to set a custom resolution model to a slice:

sl.resolution_model = my_resolution_model

The signature required for my_resolution_model is

• model_atqE = my_resolution_model.getModel(q,E) returns an object that represents the PSF at the point (q,E)
• model_atqE.ongrid(dqgrid, dEgrid) returns a matrix of PSF defined on the given q,E displacement grid