Todo

Groups

Restore select highlight, fix for children of rotated groups
Transforming on rotated shapes
Fix bounding box for rotated shapes
Allow single-selected groups to transform their children correctly
(merge transform-session and transform-single-session)
fix drift when moving children of rotated group
shift dragging arrow handles should lock to directions
arrow rotation with handles
fix ellipse when scaleX < 0 or scaleY < 0