[Development] Move math3d from QtGui to QtCore

[Laszlo Papp]

> If we move these classes out of QtGui and into a math library and then QtGui still needs to link with that library as the classes are used there. If we then start adding more domain specific classes to this math library, then the stuff that a plain UI would drag in also increases, even though it is useful only to a subset of the applications. I do not like that.
> These classes were added primarily to support graphics in Qt, like the shader programs, 3D math in relation to OpenGL, QGraphicsTransformation and Qt3D. Much of the arithmetic uses floats because it is closely related to OpenGL and our use of them. They should stay like that. For performance and for simplicity.

Aye, so much for collaboration! Let me duplicate 9X% of those classes
so we can maintain from two places. We can surely afford this since we
are a manpower army (especially looking forward in the near future
with this Nokia change).

BR,
Laszlo Papp