FileManager: Port to GTableModel/GTableView.

Replace the custom DirectoryView widget with a GTableView subclass.
This was pleasantly straightforward and it's so cool seeing the huge
increase in app quality from GTableView. :^)

Applications/FileManager/DirectoryTableView.cpp

@@ -0,0 +1,33 @@
+#include "DirectoryTableView.h"
+
+DirectoryTableView::DirectoryTableView(GWidget* parent)
+    : GTableView(parent)
+{
+    set_model(make<DirectoryTableModel>());
+}
+
+DirectoryTableView::~DirectoryTableView()
+{
+}
+
+void DirectoryTableView::open(const String& path)
+{
+    model().open(path);
+}
+
+void DirectoryTableView::model_notification(const GModelNotification& notification)
+{
+    if (notification.type() == GModelNotification::Type::ModelUpdated) {
+        set_status_message(String::format("%d item%s (%u byte%s)",
+        model().row_count(),
+        model().row_count() != 1 ? "s" : "",
+        model().bytes_in_files(),
+        model().bytes_in_files() != 1 ? "s" : ""));
+    }
+}
+
+void DirectoryTableView::set_status_message(const String& message)
+{
+    if (on_status_message)
+        on_status_message(message);
+}