Muons

Added information to full chain for the cosmic ray muon background using an approximation from IC86 Corsika files and Muon Gun weights
Instead of having the muons in the same `aeff_weight_file`, I think it might be good to have them in a separate file.
Pros (so far):
* files can be updated independently (e.g by different people)
Cons (so far):
* files could be updated inconsistently (e.g. new cuts/recos run just for neutrinos, not for muons)