Untangle saving TTI files into new file

The saving code is an attempt to be page function and page coding
agnostic so the same code can save (G)POP, (G)DRCS and MOT pages in
the future.

loadsave will be the home of page loading, URL exporting and also for
importing and exporting of other teletext file formats.

loadsave.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2020 Gavin MacGregor
+ *
+ * This file is part of QTeletextMaker.
+ *
+ * QTeletextMaker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * QTeletextMaker is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with QTeletextMaker.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef LOADSAVE_H
+#define LOADSAVE_H
+
+#include <QSaveFile>
+
+#include "document.h"
+#include "pagebase.h"
+
+int controlBitsToPS(PageBase *);
+void saveTTI(QSaveFile &, const TeletextDocument &);
+
+#endif