created disk manager class

This is a singleton class that will manage the disk cache to ensure the size
stays at sane levels.

app/render/diskmanager.h

@@ -0,0 +1,47 @@
+#ifndef DISKMANAGER_H
+#define DISKMANAGER_H
+
+#include <QObject>
+
+class DiskManager : public QObject
+{
+  Q_OBJECT
+public:
+  static void CreateInstance();
+
+  static void DestroyInstance();
+
+  static DiskManager* instance();
+
+  void Accessed(const QByteArray& hash);
+
+  void CreatedFile(const QString& file_name, const QByteArray& hash);
+
+signals:
+  void DeletedFrame(const QByteArray& hash);
+
+private:
+  DiskManager();
+
+  virtual ~DiskManager() override;
+
+  static DiskManager* instance_;
+
+  void DeleteLeastRecent();
+
+  qint64 DiskLimit();
+
+  struct HashTime {
+    QString file_name;
+    QByteArray hash;
+    qint64 access_time;
+    qint64 file_size;
+  };
+
+  QList<HashTime> disk_data_;
+
+  qint64 consumption_;
+
+};
+
+#endif // DISKMANAGER_H