Added new access methods.
Added new access methods.

This is used to prevent students from becoming mentors/org_admins and vica versa.

Patch by: Lennard de Rijk
Reviewed by: to-be-reviewed

--HG--
extra : convert_revision : svn%3A32761e7d-7263-4528-b7be-7235b26367ec/trunk%402001

SRabbelier/Melange,SRabbelier/Melange,SRabbelier/Melange,SRabbelier/Melange,SRabbelier/Melange,SRabbelier/Melange,SRabbelier/Melange,SRabbelier/Melange,SRabbelier/Melange