Refactor MIME type guessing to work without any PHP extension
Refactor MIME type guessing to work without any PHP extension

Closes #1241.

malayladu/core,malayladu/core,datitisev/core,malayladu/core,malayladu/core,datitisev/core,flarum/core,flarum/core,datitisev/core,flarum/core,datitisev/core