Add support for updates from GitHub

Update/VersionInfo.cs

@@ -1,5 +1,6 @@
 using Common.Debug;
 using System;
+using System.Net;
 using System.Xml.Linq;
 
 namespace Common.Update
@@ -10,7 +11,20 @@ namespace Common.Update
         public string InstallFile { get; set; }
         public DateTime InstallCreated { get; set; }
 
-        public static VersionInfo Load(string server, string file)
+        public static VersionInfo Load(ServerType updateServerType, string server, string file)
+        {
+            switch (updateServerType)
+            {
+                case ServerType.Generic:
+                    return LoadFile(server, file);
+                case ServerType.GitHub:
+                    return LoadGitHub(server);
+            }
+
+            return null;
+        }
+
+        private static VersionInfo LoadFile(string server, string file)
         {
             try
             {
@@ -44,5 +58,38 @@ namespace Common.Update
                 return null;
             }
         }
+
+        private static VersionInfo LoadGitHub(string server)
+        {
+            try
+            {
+                ServicePointManager.Expect100Continue = true;
+                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
+
+                using (var webClient = new WebClient())
+                {
+                    webClient.Headers.Add("User-Agent", UpdateCheck.ApplicationName);
+
+                    var json = webClient.DownloadString(server);
+
+                    var release = GitHubRelease.FromJson(json);
+
+                    var versionInfo = new VersionInfo
+                    {
+                        Version = Version.Parse(release.TagName),
+                        InstallFile = release.Assets[0].BrowserDownloadUrl,
+                        InstallCreated = release.Assets[0].CreatedAt.LocalDateTime
+                    };
+
+                    return versionInfo;
+                }
+            }
+            catch (Exception exception)
+            {
+                Tracer.WriteException(exception);
+
+                return null;
+            }
+        }
     }
 }