panels: implement a small margin on all panels to ensure the focus border is always visible

app/panel/project/project.cpp

@@ -40,8 +40,6 @@ ProjectPanel::ProjectPanel(QWidget *parent) :
   // Create main widget and its layout
   QWidget* central_widget = new QWidget(this);
   QVBoxLayout* layout = new QVBoxLayout(central_widget);
-  layout->setMargin(0);
-  //layout->setSpacing(0);
   setWidget(central_widget);
 
   // Set up project toolbar