Process key bindings in the `TimelineWidget` object instead of the `Player` object

The keystrokes are coped with in the Player object. This is due to historical reasons, because the movie player was the first part of the code implemented. The code for the TimeLineWidget object came later, and the keybindings have been kept in the Player. This is not logical, because some actions must be treated by the TimeLineWidget object, more specifically, they are related to the Indicator object. Also, keystrokes like Enter has nothing to do with the Player object. Indeed, it is used for starting the definition of an annotation.