Use PascalCase for Qt client filenames

Split FileTree.{h,cc} and FilterBar.{h,cc} files so that each class
is in its own file.

This breaks translations (some classes got renamed => context changed),
to be fixed by next commit (along with Tx sync).

qt/ColumnResizer.h

@@ -0,0 +1,41 @@
+/*
+ * This file Copyright (C) 2015 Mnemosyne LLC
+ *
+ * It may be used under the GNU GPL versions 2 or 3
+ * or any future license endorsed by Mnemosyne LLC.
+ *
+ * $Id$
+ */
+
+#ifndef QTR_COLUMN_RESIZER_H
+#define QTR_COLUMN_RESIZER_H
+
+#include <QObject>
+#include <QSet>
+
+class QGridLayout;
+class QTimer;
+
+class ColumnResizer: public QObject
+{
+    Q_OBJECT
+
+  public:
+    ColumnResizer (QObject * parent = nullptr);
+
+    void addLayout (QGridLayout * layout);
+
+    virtual bool eventFilter (QObject * object, QEvent * event);
+
+  public slots:
+    void update ();
+
+  private:
+    void scheduleUpdate ();
+
+  private:
+    QTimer * myTimer;
+    QSet<QGridLayout *> myLayouts;
+};
+
+#endif // QTR_COLUMN_RESIZER_H