Move SDK include and source to base

include/NazaraSDK/Widgets/BoxLayout.inl

@@ -0,0 +1,15 @@
+// Copyright (C) 2017 Jérôme Leclercq
+// This file is part of the "Nazara Development Kit"
+// For conditions of distribution and use, see copyright notice in Prerequisites.hpp
+
+#include <NazaraSDK/Widgets/BoxLayout.hpp>
+
+namespace Ndk
+{
+	BoxLayout::BoxLayout(BaseWidget* parent, BoxLayoutOrientation orientation) :
+	BaseWidget(parent),
+	m_orientation(orientation),
+	m_spacing(5.f)
+	{
+	}
+}