View / add adjust* methods to manipulate the view more easily

API changes:
* (breaking) the `rotate` method is gone
* the `adjustRotation`, `adjustResolution` and `adjustZoom` methods are now
  available and allow using an anchor.

This means interactions do not have to do the anchor computation themselves
and this also fix anchor computation when constraints must be applied.

src/ol/interaction/MouseWheelZoom.js

@@ -212,49 +212,7 @@ class MouseWheelZoom extends Interaction {
         view.beginInteraction();
       }
       this.trackpadTimeoutId_ = setTimeout(this.decrementInteractingHint_.bind(this), this.trackpadEventGap_);
-      let resolution = view.getResolution() * Math.pow(2, delta / this.trackpadDeltaPerZoom_);
-      const minResolution = view.getMinResolution();
-      const maxResolution = view.getMaxResolution();
-      let rebound = 0;
-      if (resolution < minResolution) {
-        resolution = Math.max(resolution, minResolution / this.trackpadZoomBuffer_);
-        rebound = 1;
-      } else if (resolution > maxResolution) {
-        resolution = Math.min(resolution, maxResolution * this.trackpadZoomBuffer_);
-        rebound = -1;
-      }
-      if (this.lastAnchor_) {
-        const center = view.calculateCenterZoom(resolution, this.lastAnchor_);
-        view.setCenter(center);
-      }
-      view.setResolution(resolution);
-
-      if (rebound === 0) {
-        const zoomDelta = delta > 0 ? -1 : 1;
-        const newZoom = view.getValidZoomLevel(view.getZoom() + zoomDelta);
-        view.animate({
-          resolution: view.getResolutionForZoom(newZoom),
-          easing: easeOut,
-          anchor: this.lastAnchor_,
-          duration: this.duration_
-        });
-      }
-
-      if (rebound > 0) {
-        view.animate({
-          resolution: minResolution,
-          easing: easeOut,
-          anchor: this.lastAnchor_,
-          duration: 500
-        });
-      } else if (rebound < 0) {
-        view.animate({
-          resolution: maxResolution,
-          easing: easeOut,
-          anchor: this.lastAnchor_,
-          duration: 500
-        });
-      }
+      view.adjustZoom(-delta / this.trackpadDeltaPerZoom_, this.lastAnchor_);
       this.startTime_ = now;
       return false;
     }