Support for stickings on individual notes

[dual-wield-ray]

Add support for the user to indicate a sticking (R, L) on a note. Per the mscx format this should be:

      <Measure>
        <voice>
          <Sticking>
            <text>R</text>
            </Sticking>
...

Currently individual notes are only a float representing their time in the measure, might need to support an optional tuple form with (time, sticking) on it.