v0.2.13

• The shape kind of an item is a dimension of the contract (L46). docs/SHAPES.md tells the rules.
• SHAPE_KINDS declares 4 kinds: rect, polygon, circle and free. Only rect has all of its geometry. The other kinds have their bounding box.
• LayoutBox.shapeKind, the cell dimension itemShape and the record field shapes are new and optional. A box without them is a rect.
• MeasureSpec.shapes and PACK_HARD_RULES give the kinds of each measure and rule. checkShapes refuses a run on a kind that a measure does not support.
• StageOption.supports.shape gives the kinds of an option. checkConfig, spaceSize and enumerateSpace take shapes. spaceShapeKinds gives the kinds of a space.
• Each input, record, hash and configId of 0.2.12 stays the same.