Add-on script for Blender version 2.80 or later to export mesh to text file for modify_tmd

- Register as an add-on in User Preferences.
  Once registered, you can export the mesh to text file for modify_tmd from the menu File -> Export -> Mesh for modify_tmd (.cfg/.txt)

  You can use the output file with modify_tmd to modify .tmd file.

- This add-on script may not work as expected as it is still being created.
