Improved Mamdani reasoning (weights+aggregation functions)

Thanks to some valuable contributions from @akdenizince, we now support weighted fuzzy rules and extended aggregation functions for Mamdani inference.
A pre-implemented probabilistic OR (probor) function was added to be used as aggregation function, along with Python built-ins (sum and max). If you have special aggregation functions, you can also pass them via the aggregation_function argument (code here, documentation here).