Some of us have probably seen the Doomsday Clock Ashcan that’s been circulating around the internet for the past few days. I've really been looking forward to this, as the integration of the Watchmen Universe into the DCU is the thing that most interested me about Rebirth.  The actual Doomsday Clock maxi-series is still a couple months out but I thought I would go ahead and set up a spoiler threa…