[Organizations] Add UI to explain admin vs. collaborator

[skofman1]

Explain the roles of Admin and Collaborator. Put tooltip on the Administrator and Collaborator dropdown.

• A collaborator can manage the organization's packages i.e. upload packages as well as create API keys to upload packages.
• An administrator can manage organization's packages. In addition, an administrator can also add/remove members from the organization, edit organization settings, accept or request package ownerships.

[scottbommarito]

We discussed this should not be a tooltip--it should be text on the edit organization page.