Base class for box containers. Arranges child [Control] nodes vertically or horizontally, and rearranges them automatically when their minimum size changes. Adds a [Control] node to the box as a spacer. If [code]begin[/code] is [code]true[/code], it will insert the [Control] node in front of all other children. The alignment of the container's children (must be one of [constant ALIGNMENT_BEGIN], [constant ALIGNMENT_CENTER], or [constant ALIGNMENT_END]).