Draft: New gestures (part 3): Add gesture recognizers and remove ClutterGestureAction

We have a new gesture recognizing framework now, but nobody uses it. Let's change that and add the important recognizer classes while replacing the old ClutterGestureActions: A click gesture, a long press gesture, and a pan gesture.

Note that API/behavior wise these are quite different from the old actions. The most important change is that the generic gesture recognizers in Clutter no longer directly change properties on actors, and instead only emit signals. While gesture implementations are not exactly discouraged from doing that, the generic ones provided by Clutter can't possibly cover all the cases of what people might want to do when eg. a pan happens, that's why these recognizers introduced here only provide signals.

Depends on !2389.