Add special noteheads used in Swiss rudimental drumming notation

[dspreadbury]

Requested by Urs Gehrig, who provided this summary of the historical context of rudimental drumming and the specific requirements:

20200131_Rudimental-Drumming-Font-v04.pdf

To summarise:

– Black notehead with small tail-less stem poking upwards out of its middle: flam – Half (white/unfilled) notehead with small tail-less stem poking upwards out of its middle: flam – Black notehead with small eighth-note stem poking upwards out of its middle: doublé – Half (white/unfilled) notehead small eighth-note stem poking upwards out of its middle: doublé

The remainder of the requirements need to be handled by dedicated features in music notation software, since they relate to the positioning of grace notes, tremolos on grace notes, the interpretation of shorthand notations and dynamics for correct playback, and so on.

[ursgehrig]

Dear Daniel. Thank you a lot for your support. Just let me know, if you have further questions. We are looking forward to a first implementation. Kind regards, Urs

[dspreadbury]

Urs Gehrig has requested some further changes to the design of these noteheads, per the following:

Technical-Noteheads-v3.pdf