WIP scorers: F1 pairwise clustering metric implementation

Probably a brief explanation is needed here. Consider a file where you have 1000 lines of code and you've imported 3 modules using wildcard. Then, if you need to find a function called `compute_something` you hope to find the source by running search in your editor. Obviously, if the function is imported using wildcard, you are not able to do it.

Moreover, using wildcard you are importing a lot of funtions, classes and variables which are unnecessary and/or should be kept private.