ImageSequences image orientation

[rgutzen]

Creating an ImageSequence object with the TiffIO currently defines the origin in the upper left corner of the image. This might be unintuitive for some users (including me). To move the origin to the lower left the images could simply be flipped in the IO using the PIL.Image.transpose(method=Image.FLIP_TOP_BOTTOM) or the numpy.flip(img, axis=-2) function. Or in the case that placing the origin into the upper-left corner is the desired behavior, this information should be added to the documentation. A third option might be to have an optional argument in the IO to determine the origin.