Block assembly objects ignore connections between different components

BlockAssembly.update() ignores connections between blocks in different connected components. For example, suppose block B supports block A (B --> A) and block D supports block C (D --> C). If a connection is made such that C supports D, we should have D --> C --> B --> A. But currently this connection is ignored.

The update() method should be extended to handle this case. This will also require a new method in BlockAssembly that updates global positions for all blocks in a connected component.