Comment 2 for bug 1250617

I think it's ok to say that this trust can be used to issue only X token even though the token can be used many times. This makes decrementing fairly trivial.

The interesting part of this would be:
 - how do we prevent that token being used to generate a new token.
 - Should a trust be able to specify an expiry delta for tokens that are generated from it or some other restrictions.