Improvements for the simulate routing tools

When using the "Route" tool that allows to simulate previous/future paths, I though of several things that would benefit the user:
- allow to swap src and destination easily (in the menu ? directly by clicking on the src/dest POIs ?)
- or even better, display both old and new A to B AND B to A?
- allow to place N src or destination (but not N to M): it's similar to the "impact on one destination" tool (which is also very useful). Also allow to swap 1 to N into N to 1.
- Additional infos needed in the left panel: the delta in timing and distance

It would be also cool to improve "Impact on one destination" in the same manner (or merge both tools ?). "Impact on one destination" allows only to simulate entering into the neighborhood not exiting. But the tool is more efficent (as you only need to drag one single point). You could image swapping src/dest by clicking on it.