This MR is addressing the request made by Marcin, https://git.xfel.eu/calibration/pycalibration/-/issues/122, to have a parameter in Jungfrau Darks to exclude the first number of trains from dark constants' processing. His analysis lead that the first trains of Jungfrau are a transient period that when we exclude we produce better dark constants
How Has This Been Tested?
Relevant Documents (optional)
Types of changes
New feature (non-breaking change which adds functionality)
