Try to give a more friendly message if anything goes wrong during

Try to give a more friendly message if anything goes wrong during
puzzle startup. The puzzle web pages now enclose the whole puzzle
(buttons, canvas, permalinks) in a div set to display:none, and
instead display an apologetic message saying 'sorry, it didn't work';
then, if we get through the whole init function without crashing, we
show the puzzle and hide the apology.

[originally from svn r9802]