Get value from vectors by index

Feature requests
2

To format code use ```javascript before the code see Hello, I am a little confused about a lot of things - #3 by Vinc3r

let v = new BABYLON.Vector3(1,2,3)
let p = new BABYLON.Vector3(4,5,6)
if (v.x > p.x) {
    //do something
} else if (v.y > p.y) {
    //do something
} else if (v.z > p.z) {
    //do something
}

For me the occasional coding advantage of using at and setAt is outweighed by the loss in readability.