Add docstrings to major functions/methods
Submitted by Gil Forcada
Link to original bug (#682679)
Description
As Damned-Lies does quite a lot of things already, it would be nice if we could get some docstrings[1] for big methods (no need to add a docstring for a 3 lines method :)
Task: review python code files scanning for big methods/classes and add some docstrings on them commenting what they do, input parameters and so on.