Bug 800402 - [email] UI: Show the number of unread messages in the message-list header after the folder name

sorta similarly, let's remove this countHeaders.  If you'd like to better understand what's going on in the function, it's totally fine to add a specific logger to track things in more detail.  Thanks to the newly landed "realtime-dangerous" logging level, you can get all that great stuff from logcat (or stdout when running on b2g-desktop).