Clean up NuRadioRecoio

[christophwelling]

The way NuRadioRecoio works right now is very confusing and can easily lead to errors. For example, the __scan_files method overwrites itself with another function that doesn't even take the same parameters the first time it is called. There has to be a better way to handle this.

[anelles]

I moved this to won't fix before the merge, because it will require significant work and will take longer. If anyone thinks we should do this before merging with NuRadioMC, please speak up.