[Important] Fixes the logic of the academy reset (#417)

The External Communicator now sends the AcademyDone properly

unity-environment/Assets/ML-Agents/Scripts/Academy.cs

 
         AgentAct();
 
+        if (done)
+        {
+            done = false;
+            maxStepReached = false;
+        }
+
         stepCount += 1;
     }
 
     {
         stepCount = 0;
         episodeCount++;
-        done = false;
-        maxStepReached = false;
         AcademyReset();
     }
 

unity-environment/Assets/ML-Agents/Scripts/ExternalCommunicator.cs

         }
         if (triedSendState.Values.All(x => x))
         {
-            if (hasSentState.Values.Any(x => x))
+            if (hasSentState.Values.Any(x => x) || academy.IsDone())
             {
                 // if all the brains listed have sent their state
                 sender.Send(AppendLength(Encoding.ASCII.GetBytes("END_OF_MESSAGE:" + (academy.IsDone() ? "True" : "False"))));