send targets are now by ID and Song has "Score" part, which is the notes for it. also, moved the model part separate of the actual gioui dependend stuff.
sorry to my future self about the code bomb; ended up too far and did not find an easy way to rewrite the history to make the steps smaller, so in the end, just squashed everything.
assume songs code it as 1 always; implementations are free to change this during compilation, but this should be a compile time flag / optimization; not a concern of song.
The global pattern table is constructed only during compilation. At this point, we can do also all sorts of optimizations / changes e.g. remove unnecessary releases and reuse patterns if there's a pattern already that could be used.
