Muons

Added information to full chain for the cosmic ray muon background using an approximation from IC86 Corsika files and Muon Gun weights
Rather then defining the muons as `cc` interactions and trying to stick with the `cc` vs. `nc` split, I'd change the output format here to have
 ```
{`nue` : {`cc` : ...
              `nc` :... }
 `nue_bar` : ...
 ...
 `muons` : { `any` : ... }
```
In that case, one would keep the current loop in `Aeff.py:get_event_rates` over neutrinos as is, and just make a separate calculation for the muons. Obsoletes some of the other change requests I've made, and is the cleanest in my opinion.