add activity log feature

MediaBrowser.Controller/Activity/IActivityRepository.cs

@@ -0,0 +1,13 @@
+using MediaBrowser.Model.Activity;
+using MediaBrowser.Model.Querying;
+using System.Threading.Tasks;
+
+namespace MediaBrowser.Controller.Activity
+{
+    public interface IActivityRepository
+    {
+        Task Create(ActivityLogEntry entry);
+
+        QueryResult<ActivityLogEntry> GetActivityLogEntries(int? startIndex, int? limit);
+    }
+}