Update changelog for release. Add missing documentation.

com.unity.perception/CHANGELOG.md

 
 ### Security
 
+## [0.1.0] - 2020-06-24
+### This is the first release of the _Perception_ package

com.unity.perception/Runtime/GroundTruth/Ego.cs

         /// </summary>
         public string Description;
         EgoHandle m_EgoHandle;
-
+        
+        /// <summary>
+        /// The EgoHandle registered with the SimulationManager at runtime.
+        /// </summary>
         public EgoHandle EgoHandle
         {
             get

com.unity.perception/Runtime/GroundTruth/PerceptionCamera.cs

 
                     if (produceRenderedObjectInfoMetric)
                         ProduceRenderedObjectInfoMetric(renderedObjectInfos, frameCount);
+
+                    //
                 });
             }
 

com.unity.perception/Runtime/GroundTruth/SimulationManager.cs

         /// Report a metric not associated with any sensor or annotation.
         /// </summary>
         /// <param name="metricDefinition">The metric definition of the metric being reported</param>
+        /// <returns>An <see cref="AsyncMetric"/> which should be used to report the metric values, potentially in a later frame</returns>
         public static AsyncMetric ReportMetricAsync(MetricDefinition metricDefinition) => SimulationState.CreateAsyncMetric(metricDefinition);
 
         /// <summary>