Review roles and permissions

[leeomara]

As the site has grown, roles and permissions have changed.

There may be value in a review

• the overall structure of the permission system (roles, teams, permissions, workflow)
• organization of roles (regular and "plus" roles)
• specific permissions for each role

This shouldn't be done before:

• Update publishers and sites admins permissions to include Moderation scheduled publish time #956
• Changes to roles and permissions #955

This came up as part of the review for #1143.