- finished migrating undo/redo system to CommandManager
 * cleaned up all related code in three-editor
 * added methods to undo/redo multiple operations (for history view)
 * added scale operation and related implementation in transform controls, so there is now full support
for scaling undo/redo/ history
- experients in three-viewer  :
 * a potentially more practical system for post processing effects
 * some key/mouse combos experimentation