Gui: Add ability to easily lock Toolbars from UI

This adds the Std_ToggleToolBarLock action mentioned in #4992. It is
exposed in the context menu of toolbar and also in the view -> toolbars
app menu.

src/Gui/ToolBarManager.cpp

@@ -408,11 +408,7 @@ void ToolBarManager::restoreState() const
         }
     }
 
-
-    hPref = App::GetApplication().GetUserParameter().GetGroup("BaseApp")
-        ->GetGroup("Preferences")->GetGroup("General");
-    bool lockToolBars = hPref->GetBool("LockToolBars", false);
-    setMovable(!lockToolBars);
+    setMovable(!areToolBarsLocked());
 }
 
 void ToolBarManager::retranslate() const
@@ -426,6 +422,30 @@ void ToolBarManager::retranslate() const
     }
 }
 
+bool Gui::ToolBarManager::areToolBarsLocked() const
+{
+    auto hPref = App::GetApplication()
+                     .GetUserParameter()
+                     .GetGroup("BaseApp")
+                     ->GetGroup("Preferences")
+                     ->GetGroup("General");
+
+    return hPref->GetBool("LockToolBars", false);
+}
+
+void Gui::ToolBarManager::setToolBarsLocked(bool locked) const
+{
+    auto hPref = App::GetApplication()
+                     .GetUserParameter()
+                     .GetGroup("BaseApp")
+                     ->GetGroup("Preferences")
+                     ->GetGroup("General");
+
+    hPref->SetBool("LockToolBars", locked);
+
+    setMovable(!locked);
+}
+
 void Gui::ToolBarManager::setMovable(bool moveable) const
 {
     for (auto& tb : toolBars()) {