PCL plane point cloud B-spline curve fitting

This C++ code utilizes the Point Cloud Library (PCL) to perform 2D curve fitting on a point cloud and visualize the results. The code includes several methods for fitting, including point distance minimization, tangent distance minimization, squared distance minimization, and their asymmetric counterparts.

**Main Function**:
— A `PointCloud` object `cloud` is created and loaded from a PCD file provided as a command-line argument.
— Command-line arguments are parsed to determine which fitting method to use.
— The point cloud is transformed to fit the default orientation expected by the curve fitting methods (xoy plane).
— The transformed point cloud is then converted to the required `vector_vec2d` format for fitting.
— An initial NURBS curve is created with a specified order and number of control points.
— Depending on the command-line arguments, a fitting object is created and solved for the best curve that fits the point cloud data.
— The fitted curve is visualized using the `VisualizeCurve` function.
— The viewer is set up with a size and a white background color.
— The original point cloud is visualized, and the fitted curve is displayed.
— The viewer runs in a loop, processing events and updating the visualization until it is stopped.