Abort

makes it possible to abort entire action from subcard

also includes other improvements to exception handling and some touch-ups
unrelated (and untested) fix.  if a structured card's db content did not match its structural content, then references were not getting updated correctly.  (eg, if you change a Basic card to a Ticket on wagn.org, in which case its db content would not come from the structure).

I think this was probably underpinning LOTS of weird bugs.