Add support to oscillations open data release

We would like to use this project to read the oscillations open data release.

For now the open data release will consist of two files.

The first one will contain information about the structure of the histograms corresponding to the response matrix of the detector (for now it is a root file containing the already built TH3D objects, in the future it could be some sort of plain text file)

The second one is a root file containing a simple flat tree which has the information on how to fill the histograms by giving the bin number on each dimension, the weight and the error on the weight.