Change default settings when adding a point

[_Aka_]

You mentor is probably right. If I had designed CurvySplineSegment from scratch, I would probably not made it a partial class. But the thing is that the class was 2900 lines of code. Discovering the class could be overwhelming for newcomers. I decided to subdivide the file in two, one with the publicly available code, and the rest in another file. This way you have a smaller file to look at if you just want to take a look at what members are available to you when using a CurvySpline (besides reading the API reference or using autocompletion).