Write changes to ES2 files

[mmatyas]

When the game data changes (favorite, play count, ...), the gamelist file should be updated. This should be done keeping plugins in mind. If there are unsupported tags and properties, it should retain them.

---

Previous issue text:

# Increase play count when a game ends

The play count field should be increased in the config files after a game ends.
This involves (re-)writing the config file.

[mmatyas]

Read-only support might be enough for now.