Implemented NamedPitch.to_staff_position(clef=None). NEW.

Removed ...

    NamedPitch.absolute_staff_position

... property. Use NamedPitch.to_staff_position() instead.

Example 1: changes C#5 to absolute staff position:

    >>> NamedPitch('C#5').to_staff_position()
    StaffPosition(number=7)

Example 2: changes C#5 to treble staff position:

    >>> NamedPitch('C#5').to_staff_position(clef=Clef('treble'))
    StaffPosition(number=1)

NEW: should be included in the 2.16 release notes.