For drums: Dynamically generates positions maps

[jmmelko]

• Add grid size argument in instrument parser __init__()
• Pass this argument to note parser
• Let note parser calculate position map or better, use a math function
• make Skygrid a class
• Skyjson
• skyabc15
• skykeyboard
• do Rémi
• doremijp
• English
• englishchords
• noteparser