Gui: AutoSaver and recovery changes

* Fix AutoSaver inconsistent BinaryBrep setting

* Use temperary name when auto saving, so that it won't overwrite the
  original file, which may cause corruption when crashing in the middel
  of auto saving, especially if auto saving in a separate thread.

* Support auto recovery document containing external links

* Do not mark success after auto recover, in case the program crash
  again before the user remember to save the just recovered file. Only
  mark when user saves the document.

src/Base/Writer.h

@@ -195,6 +195,7 @@ public:
     virtual void writeFiles(void);
 
     virtual std::ostream &Stream(void){return FileStream;}
+    void close() {FileStream.close();}
     /*!
      This method can be re-implemented in sub-classes to avoid
      to write out certain objects. The default implementation