[Draft] Fixed a bug in arc editing and added preview
[Draft] Fixed a bug in arc editing and added preview

Fixed a bug so arc editing take correctly the placement into account.
Added preliminary support for preview during arc editing. To be improved in the future.
Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master