stacked vector obs

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

   m_EditorClassIdentifier: 
   m_BrainParameters:
     vectorObservationSize: 4
-    numStackedVectorObservations: 1
+    numStackedVectorObservations: 2
     vectorActionSize: 03000000030000000300000002000000
     vectorActionDescriptions: []
     vectorActionSpaceType: 0
   m_EditorClassIdentifier: 
   m_BrainParameters:
     vectorObservationSize: 4
-    numStackedVectorObservations: 1
+    numStackedVectorObservations: 2
     vectorActionSize: 03000000030000000300000002000000
     vectorActionDescriptions: []
     vectorActionSpaceType: 0
   m_EditorClassIdentifier: 
   m_BrainParameters:
     vectorObservationSize: 4
-    numStackedVectorObservations: 1
+    numStackedVectorObservations: 2
     vectorActionSize: 03000000030000000300000002000000
     vectorActionDescriptions: []
     vectorActionSpaceType: 0