Given a map of hierarchy key->value, it will return the list of available options for all hierarchy levels
for example:
hierarchy = School, Dept, Subj
params: {School=>"", Dept=>"Dept1", Subj=>""}
return: {School=>{"school1", "school2"}, Dept=>{"Dept1"}, Subj=>{"Subj1", Subj2", "Subj3"}}