The other subfolders of tools/ had already been moved to either
editor/, misc/ or thirdparty/, so the hiding the editor code that
deep was no longer meaningful.
(Manual redo of 49c065d29c)
-ability to edit multiple scenes at the same time
-resource internal IDs are now persistent, this makes multiple scene
editing possible but maaaaay result in file corruption bugs (tested and
could not find anything but possibility exists because core code
changed, report immediately if you find this).
-properly save settings, layout, etc when edited
-script editing is independent from scene editing now
-show a yellow box when a script belongs to the scene
