Refactored util/transforms.py translate, scale and rotate to just return

Refactored translate, scale and return to just return a matrix to be multiplied instead of the matrix multiplication being done in the method

Adapted scenen linear transforms as appropriate

Adapted examples as appropriate (except for ipython notebooks, cannot test those)
I'd be in favor of two functions, since it is so much less code: if we include the feature @rossant proposes (forcing the choice of units) it would be something like:
    def rotate(x = None, degrees = None, radians = None):
        if x is not None:
            raise TypeError
        if degrees is not None and radians is not None:
            raise TypeError
        if degrees is None and radians is None:
            raise TypeError
        if degrees is not None:
            radians = degrees/180 * math.pi
        .... rest of the code

Or something similar but it will not be as simple as
def rotatedegrees(degrees, axis):
    rotateradians(degrees/180*pi, axis)

Anyway, if we want to force choosing units (since ambiguity should be avoided) rotatedegrees(...) would be just as clear as rotate(degrees = ...)

As a side note, I agree with @lcampagn 's argument that 90 degree rotations are very common and I'd rather rotate by 90 degrees than by math.pi/2 . So that would be rotated or rotatedegrees. We may even want to define xaxis = np.array((1.,0.,0.)) and similarly yaxis and zaxis?