Transform now uses matrix math

- switch Transform to use matrix math, to fix resizing rotated children
objects
- Transform.decompose() can be used to determine the rotate, scale, skew
and translate values for the Transform matrix
- Move, Resize and Rotate tool now manipulate the selectGroup object
directly - no copies
- TransformCommand fixed to copy the transforms, and now takes an
optional old transform which can be used in place of the shapes current
transform