Change admin right to not imply script right, grant script right only on wiki level

[MichaelHamann]

@surli

This is a huge consequence IMO and I’m really not a big fan of dropping this. That’s one of the big privilege of the admins of wiki to be able to install extensions, so if they now need to always requests someone else for doing this it will quickly become a pain.

I have farms of wiki such as myxwiki.org in mind here.

There is nothing that prevents you from giving the admin script right. I’m also not suggesting to change the default right setup which - from what I understand - already explicitly gives the admin group script right. My proposal just makes it possible to have users with admin but not script right as this is currently impossible.