Implement the DB

As we talk in the last reunion, the database will look like the uploaded scheme and needs to be implemented. The DB will be implemented in [mongodb](https://www.mongodb.com/) as @machetazo suggested.  ![API DB Scheme](https://raw.githubusercontent.com/TEComputerIEEE/IEEE-TEC-WebAPI/master/IEEE%20CS%20Bot%20-%20DB.png)