[editing] Leading with ContentEditable=Minimal

There's been a good deal of discussion about the value of contentEditable=minimal. Some of us think that being able to cancel all browser actions with preventDefault on all Intention events is enough, while others believe that having a single way to stop browsers from taking action makes sense. I lean in the direction of the former, but there is another consideration- it will take more time to design and build Intention events in all cases, so why not work toward making contentEditable=minimal available, and then ship Intention events once we have a more complete story ready?