Experimental Object Carrying and Throwing 0.87

Detached groups of nodes can now be carried instead of entire objects only.
That means you can pick up one brick from a brick wall or grab that bumper that fell from your drift car.

- New grabbing logic will apply forces only to the part of an object that is inside a region in front of the player, so you can try to lift one side of a long object for example.
- Included object pitch rotation (mouse middle button drag)
- Improved object position and rotation target keeping.