Stack augmentations

Presently:
At current time (1.6.46), current operation is that if you delete an item with other items on top of it, it deletes all items in the stack. I will give this default functionality a name: "Delete Stack."

I modify "Delete Stack" in that it is the action that is performed with collisions turned ON and the user deletes an item.

Delete FROM stack: With collisions turned OFF, this deletes the item, but sets everything else to hover at their current position, as though they were lifted from grade with collisions turned OFF.

Reset collision:
With collision turned back ON, and an item (or items) selected, the system ignores all items selected, and calculates the collision distance below that item, turns collision off, puts the item(s) there, and turns collision back on.

Example usage:
User constructs a table with a pyramid of individual wine glass objects, stacked with collisions turned on.
Delete stack: Deleting the table deletes the stacked pyramid, too.

Delete from stack: Deleting the table leaves the pyramid stack in place.

"Drop": We already do this when placing normal objects to some degree. I am not seeking to change how items are loaded in the scene, but am suggesting restoring that functionality to objects already in the scene.

With collisions turned OFF, "Drop" will ignore the current selection of items, calculate the next location you would otherwise normally set an item, and sets all items there, yet overlapping.

With collisions turned ON, "Drop" will loop through all items, and starting from the ones with the lowest level, drop them to the floor, and then spread them out equally until they no longer collide. Repeat until all layers of objects in the original selection are dropped downwards to the closest surface. Note, if objects are already overlapping with an object outside the collection, ignore that object in the calculations.