Add Weighted N-1 Functionality (As well as commonmasks and categorical axis injection/filling)

[NJManganelli]

This issue is to track adding, in almost identical manner to PR #1272 , the options for weights, commonmasks, and categorical axes injection for N-1 plots from PackedSelection. This should consist largely of copying and slightly tweaking the Cutflow code, adding test variations, and adding examples to the docs/notebooks.