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)
@lcampagn what do you mean? I thought this is the numpy way to do an in-place assignment. Anyway, if issue #507 is accepted, this will change to self.matrix *= transforms.scale(...)