MOF14 — Generated operations returning attributes/references should not raise Cons

Summary: The generated IDL for the MOF includes ConstraintError in
the raises clause of operations generated via the Attribute
Template and Reference Template, although these templates do
not include spcification of that exception (identified in a
separate issue). When that specification is updated, it
should specify that the generated "read" operations do not
raise this exception. The current IDL has ConstraintError
in the raises clause of the following operations, which do
not change the state of the model: