Improve rename logic for directory name collisions.

cps/helper.py

@@ -332,7 +332,12 @@ def update_dir_stucture(book_id, calibrepath):
     if titledir != new_titledir:
         try:
             new_title_path = os.path.join(os.path.dirname(path), new_titledir)
-            os.renames(path, new_title_path)
+            if not os.path.exists(new_title_path):
+                os.renames(path, new_title_path)
+            else:
+                for dir_name, subdir_list, file_list in os.walk(path):
+                    for file in file_list:
+                        os.renames(os.path.join(dir_name, file), os.path.join(new_title_path + dir_name[len(path):], file))
             path = new_title_path
             localbook.path = localbook.path.split('/')[0] + '/' + new_titledir
         except OSError as ex: