Line smoothing

[Agustin Alba Chicar]

Add line smoothing to the roads with some kind of interpolation like Bezier lines or Splines

[Agustin Alba Chicar]

@JChoclin, to sum up the research, here it is. Splines are deprecated in the next release of Gazebo in favour of Ignition Splines. Both expose a similar interface and we can use it inside the RoadCreator class its functionality. We can use some arguments to dynamically set if we want to use the interpolation and the resolution to use.

[Agustin Alba Chicar]

@andres_fortier a PR is made here if you want to track the progress.

[Javier Iván Choclin]

Added line smoothing refs #13

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