Renew the updater branch

Now with some actual consensus on what the updater will do!

mmc_updater/src/UpdateObserver.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <string>
+
+/** Base class for observers of update installation status.
+  * See UpdateInstaller::setObserver()
+  */
+class UpdateObserver
+{
+	public:
+		virtual void updateError(const std::string& errorMessage) = 0;
+		virtual void updateProgress(int percentage) = 0;
+		virtual void updateFinished() = 0;
+};
+