[Feature] shape rotation

[ndgnuh]

What has changed

• Add rotateCenter and rotateCenterBreak to Shape. rotateCenter rotate and keeps the shape, while rotateCenterBreak breaks the rectangle to create a quadrangle, then rotate it. The rotate action is a no-op on circles and points.
• Modify the canvas to rotate the shape when the mouse scroll and there are selected shapes. If the condition is not met, the scrolling falls back to the previous behavior.
• Add undo for scroll actions.
• Modify canvas and app to block the scrolling when rotating the shapes.

The shortcut:

• No modifier: rotate the shape 5deg.
• Shift modifier: rotate and break the shape.
• Ctrl modifier: rotate 30deg.

Screencap example:

labelme-rotate.mp4

[VShawn]

LGTM