Removed pitchtools.clef_and_staff_position_number_to_named_pitch(). CHANGE.

Use NamedPitch.from_clef_and_staff_position() instead.

CHANGE: should be noted in the 2.16 change log.
Removed pitchtools.apply_accidental_to_named_pitch().

Use NamedPitch.apply_accidental() instead.

CHANGE: should be noted in the 2.16 change log.
Removed pitchtools.contains_subsegment().

No alternative method provided.

The function was a five-line implementation that was not general enough to
remain in the API.

When we want this functionality again we should reimplement on the Segment
classes in a general way.

Doesn't need to be mentioned in the 2.16 change log.