Add the `vulnerability_tickets.py` sample security plugin to deny access to tickets with "security" or "vulnerability" in the `keywords` or `summary` fields.
Add the `vulnerability_tickets.py` sample security plugin to deny access to tickets with "security" or "vulnerability" in the `keywords` or `summary` fields.


git-svn-id: 0d96b0c1a6983ccc08b3732614f4d6bfcf9cbb42@5978 af82e41b-90c4-0310-8c96-b1721e28e2e2

rbaumg/trac,rbaumg/trac,rbaumg/trac,rbaumg/trac