Accelerate 3D rendering with VBO support

*First step to move Part rendering using VBO instead of direct rendering
*Update comments inside the code
*Assume VBO is available if OpenGL > 3.0 is detected
*Add initial Color support to VBO rendering !
*Initial full feature VBO rendering implementation
*Modify some include issue for linux build
*Try to fix linux include header
*Reupdate header include for linux support
*Fix compilation on linux
*Fix linux and MacoOS build
*Fix glGetString definition
*Fix Windows build
*Add VBO support as an option into the Preference menu
*Fix crash while running FreeCAD test bench with new VBO rendering infrastructure (in both cases)
*Improve performances
*Compute material index only when a VBO update is required (improve frame rate by 10%)
*Clean the code
*Fix Travis compilation warning
*Try to fix Windows compilation issue
*Update include for Windows

src/Gui/View3DInventor.cpp

@@ -177,6 +177,7 @@ View3DInventor::View3DInventor(Gui::Document* pcDocument, QWidget* parent,
     OnChange(*hGrp,"BackgroundColor4");
     OnChange(*hGrp,"UseBackgroundColorMid");
     OnChange(*hGrp,"ShowFPS");
+    OnChange(*hGrp,"useVBO");
     OnChange(*hGrp,"Orthographic");
     OnChange(*hGrp,"HeadlightColor");
     OnChange(*hGrp,"HeadlightDirection");
@@ -368,6 +369,9 @@ void View3DInventor::OnChange(ParameterGrp::SubjectType &rCaller,ParameterGrp::M
     else if (strcmp(Reason,"ShowFPS") == 0) {
         _viewer->setEnabledFPSCounter(rGrp.GetBool("ShowFPS",false));
     }
+    else if (strcmp(Reason,"useVBO") == 0) {
+	_viewer->setEnableduseVBO(rGrp.GetBool("useVBO",false));
+    }
     else if (strcmp(Reason,"Orthographic") == 0) {
         // check whether a perspective or orthogrphic camera should be set
         if (rGrp.GetBool("Orthographic", true))