images are being cut off

[falkben]

currently we crop the summed images to the largest image in the set. however, this often results in part of the final image being cut off.

we have an additional option enlarge which will enlarge the summed final image in x and y by a specific amount of pixels, but has to be configured and there's no easy way to know how much to add in x or y without trying it.

What we really want is to use maximum/minimum extents in coordinates of all the images and then project each of our summed images onto that

This will allow to remove the enlarge option, as this new behavior we should always use and would never result in a cropping.

We might need a new option to crop to the maximum extents with multiple images summed (so we don't get a lot of single image data around the edges).