Add uncertainties information

[lelaus]

A few correlations come with uncertainties specified for specific parameters. In addition, also some data come with uncertainties.

This information should be added to the results provided by lbh15. In particular, 3 kinds of uncertainties must be managed:

1. absolute uncertainties;
2. relative uncertainties;
3. uncertainties on the value of inner parameters, thus requiring to compute how they influence the value calculated with the correlation they contribute to define.

[lelaus]

In 231e068, a new folder named uncertainties has been added to the project. This folder contains the work done by @prisma34 related to the uncertainties of data and properties implemented into lbh15. Anyway, nothing of what implemented in this folder has yet been added to the lbh15 project.
This integration is yet to be done.
Once terminated this integration activity, the above-mentioned folder uncertainties will have to be removed from the project.