Changes about the way to create TimeEvent from ScenarioView.

TimeEvent is now created with a signal chain (the old way is documented in doxygen).
The methods name have been changed for clarity purpose.
Signal transport now QLineF and QRectF and transport them by value (lighter and safer).
An inversion bug corrected in TimeEventView.
Command Key is now needed to create a Timebox by drawing in a Scenario. TimeEvent is created at mouse release.
Bug Timebox's name corrected.