Make permissions more granular

Right now, the permission to access the Composer Security Checker settings form is "access administration pages". However, for site editor/content manager roles on a site, they may need access to administration pages for content, but we would not want them to access something this kind of configuration that should be reserved for site administrators.

I propose adding a new permission to the new module, "access composer security checker settings", and making access to the settings page based on that permission.