LibGUI: Add PathBreadcrumbbar

This Widget wraps both a Breadcrumbbar and a TextBox for editing the
path manually, based heavily on the existing code in FileManager.

Breadcrumbbar itself requires outside code to micro-manage what it does.
This class provides a simpler interface for it: Users don't have to
worry about segments, they just give/receive a string for the current
path.

Userland/Libraries/LibGUI/CMakeLists.txt

@@ -82,6 +82,7 @@ set(SOURCES
     OpacitySlider.cpp
     Painter.cpp
     PasswordInputDialog.cpp
+    PathBreadcrumbbar.cpp
     PersistentModelIndex.cpp
     Process.cpp
     ProcessChooser.cpp