update the readme

- 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 a refreshDependency function to refresh every dependency link (execute addDependency(this) in each parent of a child)

- create an actionSelection only when there is a selection

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

add thread class (stitch one, not computing) to deal with color, width and later (maybe) rendering style

second move to a MVC design

add a OE_svgParser class to fill the document
first move to a MVC design