change 'appspot.py show' to put summary first

Right now, 'appspot.py show' generates text that looks like:

  Issue 87065  http://codereview.appspot.com/87065
  Make any object throwable in Valija.  Addresses  issue 1036 .

The problem is that svn and other tools will show just
the first line in compact listings.  So, history summaries
end up being a series of meaningless appspot issue numbers.

This change makes appspot.py print the summary first.