Make env easier and add model

Project/Assets/ML-Agents/Examples/PushBlock/TFModels/PushBlockFreeze.onnx.meta

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+  fileIDToRecycleName:
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+    11400002: model data
+  externalObjects: {}
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+  assetBundleVariant: 
+  script: {fileID: 11500000, guid: 683b6cb6d0a474744822c888b46772c9, type: 3}
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+  forceArbitraryBatchSize: 1
+  treatErrorsAsWarnings: 0