Update improvements

Include NzbDrone.Update in mono/osx package
Do not ignore certificate warnings for services
Check hash before extracting update
New: Update support for Linux/OS X - see the wiki for more information

src/NzbDrone.Core/Update/UpdateVerificationFailedException.cs

@@ -0,0 +1,15 @@
+using NzbDrone.Common.Exceptions;
+
+namespace NzbDrone.Core.Update
+{
+    public class UpdateVerificationFailedException : NzbDroneException
+    {
+        public UpdateVerificationFailedException(string message, params object[] args) : base(message, args)
+        {
+        }
+
+        public UpdateVerificationFailedException(string message) : base(message)
+        {
+        }
+    }
+}