Outlier frac_pp

[msilvafe]

As discussed in PR #315 in this comment when running with all bands there will be slight variations in the frac_pp for tracking between the different bands and we need to run on some mean value that's slightly suboptimal for all. If one band fails there can be a large outlier that could skew this mean but also indicates that there was an issue with that band and we should go back and debug. To that end we would like to add in a flag during the uxm_setup/tracking_setup steps which flags a band with a large outlier frac_pp so that it's not included in the mean and tells the user that they should go back and fix that band.