Ditching the utterly redundant, and down right nuisance of a permission 'cms.login'

The plan at the time was to have both the front end login and CMS login driven from the same system which would make this permission useful. Now that we're not doing that, it's not
Simplifying pre-packaged roles + fixing some permissioning issues that were stopping user's form being able to access the web user management + link libarary