Peakbag output needs to be cleaned up.

[nielsenmb]

At the moment there's lots of PyMC3 stats that are output in the peakbag_summary file. I haven't been able to figure out what they mean and if they are even relevant. The only relevant values that I understand are the mean, sd, r_hat and posterior/prior width ratio.

Can we remove them?

Also we need a general description somewhere of the outputs of each stage.