Add ability to log in/sign up with social auth

[nrsimha]

It will be nice to have option to log in/sign up with social auth (e.g. Google, Github or FB).

[HappyNinja2]

@rrebase I also noticed that the forgot password option is missing. Should we create an issue for it?

[rrebase]

Yeah, please create an issue for the forgot password option.

Social auth should be done with django-allauth. It's probably not super straightforward since the project is an SPA and the templates can't be reused. Need to add/update appropriate rest API endpoints of dj-rest-auth .