normalize method
Normalize the quaternion. Note that this changes the values of the quaternion.
Implementation
Quaternion normalize(){
double l = math.sqrt(x * x + y *y + z *z + w * w);
if (l == 0) {
x = 0;
y = 0;
z = 0;
w = 0;
} else {
l = 1 / l;
x *= l;
y *= l;
z *= l;
w *= l;
}
return this;
}