update the readme

- remove the OE_commandDisplay class (specific functions are merged in OE_diplay)

- make first and last point move together when form is closed

- use it in OE_actionMovePointCurve
- clear OE_actionSetPointCurve (not used)

- add OE_controller::getSelectionBoundingBox function
- rename "select" function to "picking" in OE_interfaceDisplay (more clear name)
- change selection mode into an editionState in OE_interfaceDisplay
- add scale method to curves and stitchs
- add ScaleSelection state and implement the scale selection actions and UI widget
- clean and comment OE_interfaceDisplay
- add BoundingBox::getCenter method
- add OE_display::screenToDocument method

- add actions for moves
- add - operator to vector_2d class

- add editLastAction function to OE_controller to make possible "live modification"
- add OE_actionSetPointCurve and OE_actionMovePointCurve to OE_actionCurves
- add setPoint function to OE_pointcurve and change getPoint to use reference instead of pointer

declare dependents objects to their reference (to be able to remove the reference without error)

add a new subcurve class (parametric subcurve) and a joincurve (concatenate curves)