ludus. Changes to entity creation and initialization.

Remove the child capacity and render capacity arguments from entity creation.
Add method to set the entity child count and render count.
ludus. Separate reading object from reading object content in load tree.

This reverts a previous change that removed read object content.
This change is needed to separate object creation from object content loading.
ludus. Changes to object interface.

Add set game data method.
Remove game data argument from object creation.
Engine create object still gets game data argument, since this method is called by the game, that can supply the data.