Update to Django 1.6

Changes:
- Removed Sites framework app and SITE_ID setting because it's not on by default in 1.6
- Enabled click-jacking app because it is on by default in 1.6
- Setup ALLOWED_HOSTS setting to be populated from general.yml
- Added SESSION_COOKIE_HTTPONLY = True and CSRF_COOKIE_HTTPONLY = True because the option is now available