* use `trac.ticket.Ticket` instead of `trac.ticket.model.Ticket`
* use `trac.ticket.Query` instead of `trac.ticket.query`
* use quality `8` instead of `9`, so that it's easily possible for
the user to force the usage of a custom converter, while staying
in the 0-9 range.
* make the conversion tests more platform independant (both modified
tests failed for me on Windows)
