QMatrix4x4 operator* with QVector3D is unclear

 QVector3D documentation says `"The QVector3D class represents a vector or vertex in 3D space." `

QMatrix4x4 provides an operator* to transform a QVector3D. This has several issues:

1. Using * remembers of an algebraic operation, which is incorrect between a 4x4 matrix and a 3x1 vector. This is implement as if the QVeector3D was a QVector4D with a 1 in the w coordinate and doing the mathematical operation.
2. By doing that, it fails the purpose of QVector3D being a vector or a vertex, since its always considered a vertex. You can't consider a vector because when transforming it with a QMatrix4x4 its going to be treated as a vertex. 
3. Thee operator* remembers of the algebraic operation, so one could think that the distributive property applies, but it doesnt.

Consider the following code:

QMatrix4x4 worldMatrix;
 QVector3D p;
worldMatrix * p - worldMatrix * QVector3D(0,0,0);

 
p here is a vector, so when applying the worldMatrix transformation, I dont wan't the traslation. That is why I need to remove it with the `worldMatrix * QVector3D(0,0,0)`.

One could also consider that the code could be refactored as:

QMatrix4x4 worldMatrix;
 QVector3D p;
worldMatrix * p; // in algebra, multiplying by a null vector returns a null vector

which doesn't give the same result. 

I would suggest deprecating and removing all the non mathematical operations and use proper algebra for these operations.