Add dynamics change to crawler (#4218)

* update walker

* add dynamics change crawler

Project/Assets/ML-Agents/Examples/Crawler/Scripts/CrawlerAgent.cs

     public Material groundedMaterial;
     public Material unGroundedMaterial;
 
+    EnvironmentParameters m_ResetParams;
+
+        m_ResetParams = Academy.Instance.EnvironmentParameters;
+
+        SetResetParameters();
 
         //Setup each body part
         m_JdController.SetupBodyPart(body);
     /// </summary>
     public override void OnEpisodeBegin()
     {
+        SetResetParameters();
         foreach (var bodyPart in m_JdController.bodyPartsDict.Values)
         {
             bodyPart.Reset(bodyPart);
         {
             GetRandomTargetPos();
         }
+    }
+
+    public void SetResetParameters()
+    {
+        m_JdController.jointDampen = m_ResetParams.GetWithDefault("dampen", 3000f);
     }
 
     private void OnDrawGizmosSelected()

config/ppo_transfer/CrawlerStatic_JointDamp.yaml

+behaviors:
+  CrawlerStatic:
+    trainer_type: ppo_transfer
+    hyperparameters:
+      batch_size: 2024
+      buffer_size: 20240
+      learning_rate: 0.0003
+      beta: 0.005
+      epsilon: 0.2
+      lambd: 0.95
+      num_epoch: 3
+      learning_rate_schedule: linear
+      encoder_layers: 2
+      policy_layers: 2
+      value_layers: 2
+      feature_size: 32
+      reuse_encoder: true
+      in_epoch_alter: true
+    network_settings:
+      normalize: true
+      hidden_units: 512
+      num_layers: 3
+      vis_encode_type: simple
+    reward_signals:
+      extrinsic:
+        gamma: 0.995
+        strength: 1.0
+    keep_checkpoints: 5
+    max_steps: 10000000
+    time_horizon: 1000
+    summary_freq: 30000
+    threaded: true
+
+parameter_randomization:
+  dampen:
+    sampler_type: uniform
+    sampler_parameters:
+      min_value: 10000
+      max_value: 10000
+