Migrate global init stuff into UICommon.

This avoids code duplication in a bunch of places .
I also moved the NVIDIA Optimus export into VideoCommon.

Source/Core/UICommon/UICommon.h

@@ -0,0 +1,15 @@
+// Copyright 2014 Dolphin Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+
+#pragma once
+
+namespace UICommon
+{
+
+void Init();
+void Shutdown();
+
+void CreateDirectories();
+
+} // namespace UICommon