Add SessionAuthenticationMiddleware if available.
Add SessionAuthenticationMiddleware if available.

This was added in Django 1.7 in order to invalidate sessions on password
change.

opencorato/mapit,chris48s/mapit,Code4SA/mapit,chris48s/mapit,Code4SA/mapit,opencorato/mapit,opencorato/mapit,chris48s/mapit,Code4SA/mapit