several conditions are never reached in feature_function_activation

[sildater]

feature_function_activation in note_features.py requires some reworking. the function starts with

if isinstance(
        direction, (score.DynamicLoudnessDirection, score.DynamicTempoDirection)
    )

and within this conditional block continues to check for instances of score.ArticulationDirection which isn't a subclass of those.
Minor styling: line 787 should also check a class.
There are open todos, likely related to issue #244