add Zimmermann sharps

[bwbohl]

• accidentalQuarterToneSharpZimmermann (sharp missing lower horizontal beam)
• accidentalThreeQuarterToneSharpZimmermann (sharp with additional third horizontal beam in the middle)
• accidentalQuarterToneSharpZimmermannAndSharp (combination of accidentalQuarterToneSharpZimmermann and accidentalSharp)
  closes How are the chance for adding an accidentalQuarterToneSharpZimmermann #264

[bwbohl]

I updated the naming of the glyphs and fixed some inconsistencies. I also could provide characters for the Bravura font. How is the best way to supply those, e.g. via the GitHub Bravura repo?

[dkeenan7]

These 3 symbols should not be placed in the Stein-Zimmermann accidentals range. As Sorenallen99 mentioned here #264, The term "Stein-Zimmermann" is widely understood to refer to the defacto quartertone standard consisting of Stein's 1/4 and 3/4-tone sharps, Zimmermann's 3/4-tone flat and the 1/4-tone flat used by them both.
Search on "Stein-Zimmermann" within this page: https://en.xen.wiki/w/Chain-of-fifths_notation

It is sometimes contrasted with the Stein-Couper set, that substitutes Couper's 3/4-tone flat for Zimmermann's.
See "stc" versus "stz" here: http://www.ekmelic-music.org/en/extra/alter.php?t=24 Scroll down to read the explanations.

I suggest Zimmermann's sharps go in the "Other accidentals" range. I note that this range still has 16 unused code points. The "Other accidentals supplement" was created prematurely.

[bwbohl]

@dkeenan7 sorry for not having Had time to look into this sooner and many thanks for your qualified contribution!

I will have a look at your references and change the pull request accordingly.