Allow dragging of pageparts from 1 region to an empty retion/

Make sure the pagepart dropzones increase height when they are empty on drag & drop.
Only expand a dropzone when it's possible to drop the pagepart in the empty dropzone.

There is also a small cleanup fix in here because apparently connectedSoratable wasn't cleaned up after a drag & drop.
use $ jquery shortcut + remove another console.log
Merge pull request #86 from Kunstmaan/fix_10205_drag_pp_to_empty_region

Fix dragging of pageparts to empty region