Allow animating vec3 object3D raw position

[slecorne]

Description:
Allow animating vec3 position directly on Object3D at once.
Currently we can animate object3D position axis using property: object3D.position.z but not the complete vec3 at once.
The goal is to be able to animate the vec3 position directly through object3D without using setAttributes.
The current alternative to animate position directly through object3D is to perform 3 animations which has important performance issue.

Changes proposed:

• Adding type: position similar to raw color animation detection
• In that case animate directly vec3 object3d.position
• Tests + documentation update

Feedback welcome