Rewrite backend using Flask + mongo

[maria]

Need

Now we use Django with PostgreSQL and MongoDB, a hybrid which is hard to maintain and doesn't have much sense. Since the Django won't officially support Mongo in the upcoming releases and Flask is easier to implement with Mongo I suggest we move now, while we still can.

Solution

• Create a new directory called api
• Define a new file called app.py where our main Flask application will be defined
• Define MongoDB as the database
• Add a config file like settings.py
• Define the api as http://flask-restful-cn.readthedocs.io/en/0.3.5/
• Define api classes for each resourse
• Define routes for logging in user, logging out and api
• Remove django