Change names of behaviors

Project/Assets/ML-Agents/Examples/CubeWars/Prefabs/CubeWarArea.prefab

   m_Model: {fileID: 11400000, guid: 94b4c8f1d024049fe9cb0b180fe00229, type: 3}
   m_InferenceDevice: 0
   m_BehaviorType: 0
-  m_BehaviorName: LargeCubeSoldier
+  m_BehaviorName: Dragon
   TeamId: 1
   m_UseChildSensors: 1
   m_UseChildActuators: 1

Project/Assets/ML-Agents/Examples/CubeWars/Prefabs/SmallAgent.prefab

   m_Model: {fileID: 11400000, guid: 697e3166f993b4e4cb890de8be9ec842, type: 3}
   m_InferenceDevice: 0
   m_BehaviorType: 0
-  m_BehaviorName: SmallCubeSoldier
+  m_BehaviorName: Adventurer
   TeamId: 0
   m_UseChildSensors: 1
   m_UseChildActuators: 1

config/ppo/CubeWars.yaml

 behaviors:
-  SmallCubeSoldier:
+  Adventurer:
     trainer_type: ppo
     hyperparameters:
       batch_size: 2048
       window: 10
       play_against_latest_model_ratio: 0.5
       initial_elo: 1200.0
-  LargeCubeSoldier:
+  Dragon:
     trainer_type: ppo
     hyperparameters:
       batch_size: 2048