Filter on unread messages

[presianbg]

Is your feature request related to a problem? Please describe.
Can't find who is "spamming" my inbox. By spamming i mean a lot of legit e-mails, but for some reason not filtered and moved to the correct subfolder. It would be nice to have stats about the unread messages on a given folder.

Describe the solution you'd like
Just a tick box that remove the read messages from the statistics.

Describe alternatives you've considered
ThunderStats does the job with their custom view.

Additional context

[devmount]

This could be implemented another filter. Gets on the list. Thanks for this suggestion!