Add capacity to add a point outside of the current polyline

It was only possible to add a point on a current line and move it.
It is now possible to insert a point everywhere, a line will be created between this point and the last existing one.
The mouse interaction for this feature is Alt + LeftClick.
When the first handle was previously selected, the new point is pushed in front of the point list, otherwise, it is pushed after the last one.
This MR also brings a new version of interactor event recorder in order to handle alt modifier.
Please, note that some window manager (like KDE) already define alt + left click event, it must be disabled to use this feature.