Use normalized volume (0..1) instead of percent volume (0..100)
Add accessors for Velocity to Listener and SoundSource
Add accessors for Direction and cone properties to SoundSource
Add accessors for listener's up-vector
Add Quaternion class for 3D rotations
Add Transform3D class; modify Transform to support
Merge branch 'master' of https://github.com/LaurentGomila/SFML into custom