doc/conf.py executes generated python scripts, consider importing them

[bast]

However to do this the generated code would need to be wrapped in a function. I poked into some of these scripts (I didn't check what exactly they do) and they execute in the main scope.

[robertodr]

Points to consider when refactoring the bar chart generation code:

• Drop dependency on PyYAML. This is used to write out and read in the results from the cloc.pl script.
• Drop dependency on Pygments. Currently needed to correctly infer what's the programming language of a given source code subdirectory. This helps parsing the output of the cloc.pl script.