Added school_type and grade property to Student model.
Added school_type and grade property to Student model.

A GAE Task will be provided to update the existing entities in a later commit.

Reviewed by: Lennard de Rijk

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