#178 choose which type of mail is displayed in trainer (h/s/u)

[Samuel Wright]

I have trained my filter extesnivly to the point where
it has a 100 percent hit rate on spam, but still quite
a few unsures.

I would like to train it only on ham/unsures to try to
improve on this result.

It would be good if you could auto discard 1 type of
email (in my case spam) so I don't have to do it
manually in the web interface.

Cheers
Sam