* [rshapes] Fix multisegment Bezier splines.

It seems to me that these functions are wrong, if you step the index by 1 you move to a control point instead of the next segment.

* Fix example shapes/shapes_splines_drawing for bezier splines.

* Draw circles to fill gaps between bezier segments.

RENAMED: `DrawLine<spline_type>()` to `DrawSpline<spline_type>()` for more consistent and clear naming
REVIEWED: Bezier drawing parameters order, more consistent
REVIEWED: Spline-based examples -WIP-