- add some "const" in utils.h

- add a lot of displayStyle variables

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

- 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

- display the bounding box of the selection

- now discretized points are stored in a new 2d point type "vector_2dt" witch store the t parameter too

add a maxlen option for the birail stitch (add intermediate point when a stitch is longer than maxlen)