Only update config when version number is highers

[michaelaye]

Currently, each new start of PLPY creates a new backup file for checking and updating the TOML with
potential new entries.
But there are no new entries in the package TOML, so why is this happening so often?
The other time the config file is of course updated is for a new index.
But better to check the PLPY version and store it, so that only a new PLPY version triggers a check for
new server URLS in the config file.