Create SparkleUpdater class for access from Qt/C++

To actually get automatic updates going, all that needs to happen is that `SparkleUpdater` needs to be initialized.

The rest of the functions can be connected to elements in the UI.

launcher/Application.cpp

@@ -544,6 +544,7 @@ Application::Application(int &argc, char **argv) : QApplication(argc, argv)
     {
         m_settings.reset(new INISettingsObject(BuildConfig.LAUNCHER_CONFIGFILE, this));
         // Updates
+        // Multiple channels are separated by spaces
         m_settings->registerSetting("UpdateChannel", BuildConfig.VERSION_CHANNEL);
         m_settings->registerSetting("AutoUpdate", true);