Updating config files

[ColinHDev]

As pointed out to me by @supercrafter333 via. discord DMs a few days ago, it is annoying to currently keep the config.yml and language files up to date.
Since this plugin is still in the development stage, a fix for this does not need to be implemented immediately.
But once this plugin gets officially released, server owners should get notified when their files are outdated.

I am thinking about adding some type of "file version": A simple number which would only increase if the file needs to be updated, so there would be no increase if e.g. someone fixed a typo. And if the version of the saved file does not match the one of the plugin, it would rename the old file to e.g. old_config.yml and set the new config file in its place.