Disable "powered by" for paid accounts#630

First version will allow disabling it via settings.

Second version will disable it for all paid accounts.

I need to disable it on my website, please do this quickly ! Thanks you very much !

You can disable via settings > interface > Uncheck: Show “Powered by You Need A Wiki” for shared wikis

I have tried this (new user) and it resets the wiki (all other saved settings go back to default)