refactor(Polar): do not use private properties

The use of private properties complicates the interaction with Rotare.
So we simply get rid of it now and put all properties public.

This is probably something that we will do anyway in a later stage in
order to simplify development.

+af_tools/@Polar/Polar.m

@@ -67,7 +67,8 @@ classdef Polar < handle
     % Issues: https://gitlab.uliege.be/am-dept/matlab_airfoil_toolbox/-/issues
     % ----------------------------------------------------------------------------------------------
 
-    properties (SetAccess = private)
+    properties % (SetAccess = private)
+        airfoil  (1, :) % Airfoil name
         reynolds (1, :) double {mustBeNonnegative} % Rynolds number, [-]
         mach     (1, :) double {mustBeNonnegative} % Mach number, [-]
         nCrit    (1, :) double {mustBeNonnegative} % nCrit number, [-]