Allow users to only see tickets they are associated with.

There are three new permissions for this plugin: TICKET_VIEW_REPORTER,
TICKET_VIEW_CC, and TICKET_VIEW_OWNER. TICKET_VIEW_SELF is an alias
for all three of these.

With each permission, users will only be able to see tickets where they are
the person mentioned in the permission. So if a user has TICKET_VIEW_REPORTER,
they can only see tickets they reported. For TICKET_VIEW_CC, they just have to
be included in the CC list. 

WWW:	http://trac-hacks.org/wiki/PrivateTicketsPlugin