Center refinement using powder diffraction data

This implements refinement of beam position and camera length using powder diffraction data.

This includes:

1. the tool to average images over a given run.
2. the tool to find beam position and camera length

The powder diffraction processing algorithm includes:

1. estimation of shadow mask
2. image binarization
3. indexing of the rings with respect to a given calibrant
4. fitting circles to the extracted rings
5. refinement of camera length

Visualization provides:

1. Plot of extracted rings and fitted circles
2. Radial profile with respect to refined beam center