Make 'python manage.py runserver' commands work with either GAE SDK 1.7.5 running dev_appserver, or devappserver2 0.8.
Currently we detect between dev_appserver and devappserver2 based on availability of certain modules.
In SDK 1.7.5, both dev_appserver and devappserver2 are available, and we default to dev_appserver for backwards compatibility.  Does not have a current way to force devappserver2 in this case.