Disallow multiple jobs with the same name

This has been deprecated since a8db32983969b9b1f11a3bedb2bb8cd2d04a9465.

Issue #60.

Created by  Eelco Dolstra  on September 24, 2014
R42G3IBQUDLFWG65UX7T35MI4KTUTHNWU5EABND3N7XB66GTBQIAC
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