Improve db

#8 @gsathya @ben-jones 
I changed directory structure and split server.py into models and views.
This is how I am doing user roles for the db-> foreign keys into a table that links Users and Roles. This lets users have multiple roles and lets us add more content to the roles later. If you have a better pattern, that's fine, but I want to be able to support multiple roles per user and visa versa