float Size
Size of this node. This works differently depending on whether the node is a leaf node (no children) or a container node (has children):
Leaf nodes must ALWAYS have a non-zero size.
Container nodes with size of zero will have their size determined automatically by the sum of their child sizes
Container nodes with a non-zero size will override their child sizes and always have the explicitly set size. Sizes of children will still be used to proportionately scale the size of the child nodes within this container.