Implementation of the crossing node functionality: [Legend --> clicked node: the node that the user selected. crossed node: the node that the clicked node crossed] - We look if the 4 corners of the clicked node, crossed any other node (or link at this commit). - When a clicked node is moved around, we look from nodes that this node is crossing. If it is crossing a node then the new node is highlighted (selected). - When the clicked node is exiting the crossed node, the crossed node is un-highlighted (unselected). - If the clicked node is left inside a crossed node, then a "Group!!!" message is logged. The place were this takes place is where we should put the group function.