Smooth plan for continuous movements

[GeorgJohn]

Since plans are created from segments between waypoints, it is not guaranteed that the plans will be smooth. Means the plans can proceed without stopping the robot and changing direction on the spot.

So having a plug-in that smoothes plans would be fun. Inspiration also comes from Nav2 concepts.

[GeorgJohn]

As a first approach, it is planned to create an interface in MBF and to add the concrete realization in the repository outdoor_navigation.

Details can be found in the sub-issues.