ExtraStatics deprecated 3.1

[mmichelli]

[User Deprecated] extraStatics deprecated.

Just define statics on your extension, or use get_extra_config.

[wernerkrauss]

See https://github.com/mmichelli/TranslatableDataObject/commit/36df0fcf40431af53688884b940586d90d9dfc3b as this didn't convert into a pull request.