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/Applications/Calculator/main.cpp

@@ -30,7 +30,7 @@
 #include <LibGUI/Clipboard.h>
 #include <LibGUI/Icon.h>
 #include <LibGUI/Menu.h>
-#include <LibGUI/MenuBar.h>
+#include <LibGUI/Menubar.h>
 #include <LibGUI/Window.h>
 #include <LibGfx/Bitmap.h>
 #include <stdio.h>
@@ -69,7 +69,7 @@ int main(int argc, char** argv)
     window->show();
     window->set_icon(app_icon.bitmap_for_size(16));
 
-    auto menubar = GUI::MenuBar::construct();
+    auto menubar = GUI::Menubar::construct();
 
     auto& app_menu = menubar->add_menu("&File");
     app_menu.add_action(GUI::CommonActions::make_quit_action([](auto&) {