Refactor bandwidth file generation code

Initially, v3bwfile.py was just converting measurement Results to a Bandwidth file lines format. Then we started to apply scaling methods and filtering the measurements to satisfy certain restrictions. To don not have to modify code in other file/classes, all of that was implemented in v3bwfile.py classes/methods, but it should be moved to either an intermediate file/classes that deal with the statistics calculations (and not the format) or modify Results to be able to perform those calculations.

Edit: fix typo