Fix problems with installing econsensus for first time (https://aptivate.kanbantool.com/boards/5986-econsensus#tasks-1260285)

Created by: jogwen

• don't override entirety of deploy command in localtasks.py as it will (and has) get out of date. Instead, use main tasklib.deploy function (including git submodule commands) and define only post_deploy commands in localtasks.py
• the tests for whether we want to load env-specific data for auth_user and django_sites now take into account:
  • the fact that django-guardian specifies a post_syncdb signal handler to create an User called AnonymousUser, so on first deploy, the table won't be empty, but does need initializing
  • the fact that django.contrib.sites specifies a post_syncdb signal handler to create an example.com Site object with id=1, so on first deploy, the table won't be empty, but does need initializing