Add a Mark as Unread button to Inbox

[tpeebs]

This is a request for another shortcut button so you don't have to go
to "more actions" first. A similar labs feature exists for "mark read"

[erick...@gmail.com]

I agree, this feature would be great. I've been searching for it and
stumbled across this thread, so figured I'd throw in my support for
this feature as well.
Thanks