Convert plane positions to plane position slide sequence

[thomas-albrecht]

Here is a new branch to fix #231

[CPBridge]

Thanks!

(For future reference, it may have been easier to simply git rebase and git push -f (force push) on your existing pull request.)

[thomas-albrecht]

Thanks for the tip. I typically always just merge and never rebase.
But that makes a lot of sense. I would have needed the -f because rebase messes with the history somehow.