Generic Power Law Module?

[kbruegge]

So I made a more generic power law module for my other project. I use it for reweighing events based on different spectra. I don't think its written in a very pythonic way but it was certainly very useful for me and could be expanded upon I hope.
You can find it here in streams-cta
I'm not sure where to put this. Maybe pyfact? However since its not only working for fact we might want to put it in here?

@maxnoe @jebuss what do you guys think about a class like that anyways. Have you created similar things in the past? I would like to avoid duplication here. And also I think this needs to be done in a more pythonic way than the weird class structure I have there right now.

Heres two example plots for which I used this module. Rewighting and getting expected events and such.

trigger_efficiency.pdf
crab_efficiency.pdf

[maxnoe]

I have started something similar in my private repo for the analysis. Wanted also to put this into the pyfact.analysis module.