[Development] Move math3d from QtGui to QtCore

[Laszlo Papp]

> The float version is a simplified duplicate of QVector3D. Is this really the right way to go?

You should really consider in QtGui to use 3D point base in the
future, and extend that with your math wishes.

> And how useful is really the integer version? There is almost no 3D math that works with integer only arithmetics.

If there is a point representing 2d with integers, I do not see the
problem with having the analogy for 3D. Please note that, tracking
coordinates itself has nothing to do with math. It can be used outside
that area as well.

Best Regards,
Laszlo Papp