Add code for plots/update functions associated with normalize, average, prepare, and benchmark

[tacazares]

We currently only produce plots for train and benchmark. It would be nice to add some additional plotting functions.

• Plot bar plot of max values across chromosomes in normalize
• Fix the broken benchmark plot
• Beautify the train plot for loss and dice coefficient
• Plot the training ROI statistics?
• We could plot the Pearson correlation as heatmaps or scatterplots for the replicates going into average
• We could plot specific signal track regions in predict if an ROI is given
• We could add QC figures to prepare such as fragment length distribution and TSS enrichment
• Add code for visualizing ROI specific predictions using variants