Cargo implementation

[spacek531]

Currently there are CARGO type objects but no logic supporting them.

This thread is for discussing how these might be implemented.

[spacek531]

The simplest way would be:

• add an index property to the cargo
• add a number-of-cargo-frames property to the body

Users would still have to set the number of animation frames manually, but the script would automatically handle setting the cargo to renderable or not based on the object's index, the current animation frame, and the number of cargo frames. Users would have to keyframe the position based on the animation frame.