Everywhere: It's now "Foobar", not "FooBar", and not "foo bar"

I hereby declare these to be full nouns that we don't split,
neither by space, nor by underscore:

- Breadcrumbbar
- Coolbar
- Menubar
- Progressbar
- Scrollbar
- Statusbar
- Taskbar
- Toolbar

This patch makes everything consistent by replacing every other variant
of these with the proper one. :^)

Userland/Libraries/LibGUI/Menu.h

@@ -66,7 +66,7 @@ public:
     bool is_visible() const { return m_visible; }
 
 private:
-    friend class MenuBar;
+    friend class Menubar;
 
     int realize_menu(RefPtr<Action> default_action = nullptr);
     void unrealize_menu();