Performances to-do list

[Lauloque]

• Core: Minimize Blender Operator Calls #54 completed in fe996a2
• Core: Iterate over keyframes instead of each frame #56 completed in fe996a2
• Core: Explore ways of multithreading #57
• Core: Replace Addon dependency by direct matrix maths #48
• Core: batch process all bones at each frame #55