Added a "both sides" option for the Line command to make it a bit easier to draw a line starting from the midpoint.

Added a new BoundingBox command which can be set up on a keyboard shortcut, which will create a bounding box (either a 3D solid box, or a 2D rectangle curve) framed around the current selection.

Added a new BoundingBoxCenter command which can be set up on a keyboard shortcut, which will create a point object to mark the center of the bounding box framed around the current selection.