added command to update backends
use dev_appserver_import_hook instead of dev_appserver
use google_sql.GOOGLE_SQL_EXTRA_PATHS instead of dev_appserver
Merge branch 'dev_appserver_import_hook'
deploy has been fixed
Merge branch 'master' of https://github.com/kyakovenko/django-rocket-engine

Conflicts:
	rocket_engine/__init__.py
	rocket_engine/management/commands/appengine.py