Fixed "Simulink encountered an error while allocating a handle object…

… in MATLAB System block"

- The error was occuring only after upgrade to MATLAB 2020b.
  (Check #15)
- Removed parent class "handle" from KinDynComputations class definition.
- Saved changes in 2020b format file `robotDynamicsWithContacts_lib_2020b.slx`.
- Exported changes in 2019b format file `robotDynamicsWithContacts_lib.slx`.
- Renamed test model files adding respective suffixes 2019b, 2020a and 2020b.
  (test models content haven't changed apart from the Simulink version)

lib/+iDynTree2WBTmappers/KinDynComputations.m

@@ -1,4 +1,4 @@
-classdef KinDynComputations < handle
+classdef KinDynComputations
     %KINDYNCOMPUTATIONS The calss wraps the iDynTree::KinDynComputations methods using Simulink function calls.
     %   Detailed explanation goes here
 
@@ -14,7 +14,7 @@
         function obj = KinDynComputations()
         end
 
-        function setRobotState(obj,w_H_b,s,base_pose_dot,s_dot)
+        function obj = setRobotState(obj,w_H_b,s,base_pose_dot,s_dot)
             % Sets the robot state the wrapper methods depend on
             [obj.w_H_b,obj.s,obj.base_pose_dot,obj.s_dot] = deal(w_H_b,s,base_pose_dot,s_dot);
             obj.NDOF = numel(s_dot);

lib/+wbs/@Robot/Robot.m

@@ -52,7 +52,7 @@ function set_robot_state(obj, w_H_b, s, base_pose_dot, s_dot)
             %        - s = [NDOF, 1] Joints position vector
             %        - base_pose_dot = [6,1] linear and angular velocity of the base
             %        - s_dot = [NDOF, 1] Joints velocity vector
-            obj.KinDynModel.kinDynComp.setRobotState(w_H_b, s, base_pose_dot, s_dot);
+            obj.KinDynModel.kinDynComp = obj.KinDynModel.kinDynComp.setRobotState(w_H_b, s, base_pose_dot, s_dot);
         end
 
         function M = get_mass_matrix(obj,motorInertias)

lib/RobotDynamicsWithContacts/+robotDynWC/step_block.m

@@ -2,11 +2,8 @@
     % step_block This block takes as input the joint torques and the
     % applied external forces and evolves the state of the robot
 
-    properties
-        robot_config = struct();
-    end
-
     properties (Nontunable)
+        robot_config;
         contact_config;
         physics_config;
         OutputBusName = 'bus_name';