Read the index, and load the document list from it

        Arguments:
            callback --- called during the indexation (may be called *often*).
                step : DocSearch.INDEX_STEP_READING or
                    DocSearch.INDEX_STEP_SORTING
                progression : how many elements done yet
                total : number of elements to do
                document (only if step == DocSearch.INDEX_STEP_READING): file
                    being read

def reload_index(self, progress_cb=dummy_progress_cb):
        """
        Read the index, and load the document list from it

        Arguments:
            callback --- called during the indexation (may be called *often*).
                step : DocSearch.INDEX_STEP_READING or
                    DocSearch.INDEX_STEP_SORTING
                progression : how many elements done yet
                total : number of elements to do
                document (only if step == DocSearch.INDEX_STEP_READING): file
                    being read
        """
        nb_results = self.index.start_reload_index()
        progress = 0
        while self.index.continue_reload_index():
            progress_cb(progress, nb_results, self.INDEX_STEP_LOADING)
            progress += 1
        progress_cb(1, 1, self.INDEX_STEP_LOADING)
        self.index.end_reload_index()