add new nn files and update prefabs

Project/Assets/ML-Agents/Examples/Crawler/Prefabs/DynamicPlatform.prefab

         type: 3}
       propertyPath: m_Model
       value: 
-      objectReference: {fileID: 11400000, guid: bc88124bd90354dafa003eef1047c8e9,
+      objectReference: {fileID: 11400000, guid: 87bf6e217025144c2a0168ee4bd2466d,
         type: 3}
     - target: {fileID: 4845971001715176649, guid: 0456c89e8c9c243d595b039fe7aa0bf9,
         type: 3}

Project/Assets/ML-Agents/Examples/Crawler/Prefabs/FixedPlatform.prefab

         type: 3}
       propertyPath: m_Model
       value: 
-      objectReference: {fileID: 11400000, guid: 701c1ba5d3dc741b1bb34b2f8a597803,
+      objectReference: {fileID: 11400000, guid: c6509001ba679447fba27f894761c3ba,
         type: 3}
     - target: {fileID: 4845971001715176649, guid: 0456c89e8c9c243d595b039fe7aa0bf9,
         type: 3}

Project/Assets/ML-Agents/Examples/Crawler/TFModels/CrawlerDynamic.nn.meta

 fileFormatVersion: 2
-guid: bc88124bd90354dafa003eef1047c8e9
+guid: 87bf6e217025144c2a0168ee4bd2466d
 ScriptedImporter:
   fileIDToRecycleName:
     11400000: main obj

Project/Assets/ML-Agents/Examples/Crawler/TFModels/CrawlerStatic.nn.meta

 fileFormatVersion: 2
-guid: 701c1ba5d3dc741b1bb34b2f8a597803
+guid: c6509001ba679447fba27f894761c3ba
 ScriptedImporter:
   fileIDToRecycleName:
     11400000: main obj