Add basic rotation & scaling & pivoting

[WilliamQiufeng]

Resolves #162

This PR adds scaling and rotation around a pivot for any drawables, not limited to sprites.
Changes & Features:

• We use matrix calculation now, there might be performance issues, but its not obvious
• Rotation and scaling applies to their descendents
• Sprites have IndependentRotation now, which when set fixes the rotation of the sprite
• Merging this change will require Quaver's menu visualiser bar to have IndependentRotation set, and no other observable change needs to be done at the point
• This will enable the capability of letterboxing and scaling gameplay view down so it can contain more people on the same screen.