Drag and drop sorting of pages causes unnecessary re-publish of siblings

Steps to reproduce

In CMS 6R2 the sort index when moving pages was calculated by taking the previous sibling and appending +1 which is many cases required 1 publish as long as another page was not moved to the same spot. As of CMS 7 (bugfix 89125) it is calculated by taking the sort index from the sibling at the new position and then moving ALL the existing siblings with a higher sort index.

A more optimal algorithm would be to place the moved item exactly in between the 2 siblings instead, whenever possible.