[feature] Refactor Reinhart sky discretization

Summary

Refactor to improve time efficiency.

Current behavior

I used pandas concat method in a loop, which is notoriously inefficient ...

Desired behavior

In the for loop : append dictionaries to a list, then after the loop, convert the list of dictionaries into a pandas dataframe. It reduces computing time by a factor of 10 on my computer.

Sources

https://stackoverflow.com/a/36489724

Linked features or branches

#116 (closed)

#124