implemented weighted scoring

Very useful class, I like the name, too! We should probably move the list view code (grouping issues by file etc) here too. And we might want to discuss when we are just using `array_filter` and such and when we will be using pinq. Probably only ping if more than one operation (sorting + filtering) is done, or things not supported by php natively (like grouping). @DavidBadura ping :smile: You implemented the list view grouping, how about moving that logic here? Or am I "on the woodway"?