handle cancel of adding included cards

handle cancel of adding included cards+status

handle cancel of adding included cards+priority

handle cancel of adding included cards+tag

handle cancel of adding included cards+commit

handle cancel of adding included cards+issues

We want it to just go back to the gray "Add |cardname|" right? Or at least not show this error message.

On http://test.dwagn.org/wagn/include_a_pointer click to add the card, then cancel. You'll see: "i am an included card - unknown card view: 'content_missing'"

I think this may be specific to cards in content view. regardless, yah, we want to fix this.