Refactor scoring functions.
The HeuristicScore class, which enables filter-based short-circuiting and alias heuristics for score functions.
The filter_functions.score_with_heuristics function; replaced by the more general HeuristicScore class.
Make translation.factory module public.
Rename MappingScoreFunction -> ScoreFunction.
Add a third mandatory context parameter to all mapping functions. The source argument has been removed.
Fix handling logging of duplicate source discovery in MultiFetcher.
Allow empty fetching section in main config file when extra_fetchers are given.