Implemented UI plugin downloading

MediaBrowser.Api/HttpHandlers/PluginAssemblyHandler.cs

@@ -0,0 +1,31 @@
+using System;
+using System.IO;
+using System.Net;
+using System.Threading.Tasks;
+using MediaBrowser.Common.Net.Handlers;
+using MediaBrowser.Controller;
+
+namespace MediaBrowser.Api.HttpHandlers
+{
+    class PluginAssemblyHandler : BaseHandler
+    {
+        public override Task<string> GetContentType()
+        {
+            throw new NotImplementedException();
+        }
+
+        protected override Task WriteResponseToOutputStream(Stream stream)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override Task ProcessRequest(HttpListenerContext ctx)
+        {
+            string filename = ctx.Request.QueryString["assemblyfilename"];
+
+            string path = Path.Combine(Kernel.Instance.ApplicationPaths.PluginsPath, filename);
+
+            return new StaticFileHandler() { Path = path }.ProcessRequest(ctx);
+        }
+    }
+}