Move the plugin examples to subdir of pluginhowto.

doc/pluginhowto/examples/dirmodelplugin/filesystemmodel.h

@@ -0,0 +1,17 @@
+#ifndef FILESYSTEMMODEL_H
+#define FILESYSTEMMODEL_H
+
+#include <QFileSystemModel>
+
+/**
+  This FileSystemModel is subcalss of QFileSystemModel which just returns only 1 column.
+*/
+class FileSystemModel : public QFileSystemModel
+{
+public:
+    FileSystemModel(QObject* parent=0);
+    ~FileSystemModel();
+    int columnCount(const QModelIndex &parent = QModelIndex()) const;
+};
+
+#endif // FILESYSTEMMODEL_H