Base abstract class to support gesture-specific classes.
A gesture object holds the current state of that gesture (i.e. whether the gesture has
just been started, it is in progress or it has finished) along with any gesture-specific
information it needs (like the number of taps so far, to detect triple-taps, for example).
Typically this class is not used directly, instead, some sub-class of it (like
@Efl.Canvas.Gesture_Tap or @Efl.Canvas.Gesture_Zoom) is retrieved from gesture events
(like @[Efl.Gesture.Events.gesture,tap] or @[Efl.Gesture.Events.gesture,zoom]).