Add Google Analytics Opt-Out

[JosephMDavis]

1. Add a setting in Site Settings to allow site owners to decide if users can opt-out of google analytics tracking. This setting should just be a role selector, if no roles are selected, the next setting is not enabled.
2. Add a setting to User Profile to allow users to opt-out of Google Analytics. If Google Analytics is not enabled or the Opt-Out option isn't enabled in Site Settings, this setting is not shown.