Labels

Time to explain the labels properly ;-)

This needs review and comments - half the labels is unclear and I bet half of those can and should be removed.

Also, I didn't add all the "v7.x" and "7.0-current" labels yet. What do they mean?

@karlitschek @MorrisJobke 
I think it's when there's a specific behavior that we don't want or don't have time to fix.
That behavior needs to be documented in the release notes.