This MR adds the following:
1: follow-ups from #68 (closed) and #69 (closed). Closes #68 (closed) and #69 (closed).
2: Adding the possibility to define cuts based on a variable (like in preprocessing) for the evaluation. When the samples (test samples) are loaded for evaluation, the cut is applied to the jets (only working with jet variables).
3: Update of the preprocessing documentation (preprocessing.md).
4: Fixes in the plotting code (Caps of labels, linewidth, etc.)