Position of adding Splitters

[tomczak]

I'm sure there is logic to it, but it surprises me every time:

Add Side Branch adds splitter below the current image. Clone Side Branch adds splitter above the current image.

[jsachs]

If Add Side Branch inserted above, it would not work for top level images.

If Clone Side Branch added below, it would not clone the current image.

[jsachs]

For the next release, renamed the commands to make it clearer when the splitter is inserted after the current image.