Added clarifications to the white list guidance regarding teams using 3rd party contractors

Added 3 paragraphs explaining Whitelist interactions with 3rd party collaborators.

In this case, there would be no changes to the ways that Undergrad of Overgraduate teams can operate, but would preclude High School students from Animal Use work (internally, or via a 3rd party) and the application of this principle would extend to preventing High School teams from using 3rd parties to complete any non-whitelisted work because the teams do not have access to Check-In Forms.