Add dimension re-ordering support to `to_dataset()` method

[elevans]

We can do better here and detect what the input image is and take the appropriate steps to re-order the dataset. If you try to re-order an imglib2 image with to_dataset(img, dim_order=['X', 'Y', 'Channel']) only the first two dimensions will be appropriately assigned. All other dimensions are discarded and unknown is assigned as the dimension label.