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/Forward.h

@@ -58,7 +58,7 @@ class Label;
 class Layout;
 class ListView;
 class Menu;
-class MenuBar;
+class Menubar;
 class MenuItem;
 class Model;
 class ModelEditingDelegate;
@@ -73,14 +73,14 @@ class RadioButton;
 class ResizeCorner;
 class ResizeEvent;
 class ScreenRectChangeEvent;
-class ScrollBar;
+class Scrollbar;
 class ScrollableWidget;
 class Slider;
 class SortingProxyModel;
 class SpinBox;
 class Splitter;
 class StackWidget;
-class StatusBar;
+class Statusbar;
 class TabWidget;
 class TableView;
 class TextBox;
@@ -90,8 +90,8 @@ struct TextDocumentSpan;
 class TextDocumentUndoCommand;
 class TextEditor;
 class ThemeChangeEvent;
-class ToolBar;
-class ToolBarContainer;
+class Toolbar;
+class ToolbarContainer;
 class TreeView;
 class Variant;
 class VerticalBoxLayout;