Fixing Error messages + Docs

This MR adds:

1: Update for Docs to new preprocessing etc. (DIPS, Evaluate without trained model and plotting_umami).
2: Moving the confusion matrix plotting to the plot function and clean a bit the plotting configs.
3: Update the unit test for LoadJetsFromFile and LoadTrksFromFile.
4: Improve the error message that is shown when file/files could not be found in the evaluation process.