App: use forward declaration to reduce compile time

src/Mod/Sketcher/App/SketchObject.cpp

@@ -65,7 +65,10 @@
 
 #include <App/Application.h>
 #include <App/Document.h>
+#include <App/Expression.h>
 #include <App/FeaturePythonPyImp.h>
+#include <App/ObjectIdentifier.h>
+#include <App/OriginFeature.h>
 #include <App/Part.h>
 #include <Base/Writer.h>
 #include <Base/Reader.h>
@@ -73,8 +76,6 @@
 #include <Base/Console.h>
 #include <Base/Vector3D.h>
 
-#include <App/OriginFeature.h>
-
 #include <Mod/Part/App/Geometry.h>
 #include <Mod/Part/App/DatumFeature.h>
 #include <Mod/Part/App/BodyBase.h>