Code review comment for lp:~mjs7231/do-plugins/files-folders-extensions

I can't link it like normally because they are attached to the wrong project, but the following blueprints may be solved by this update. I would argue that also including a blacklist would be a bit confusing to the UI at this point.

https://blueprints.launchpad.net/do/+spec/files-plugin-filetypes
https://blueprints.launchpad.net/do/+spec/gnome-do-file-types