Added chisubmit-server entry point
Moved backend code to chisubmit.* package
Encapsulate Flask server in ChisubmitServer class
Added missing dependency for manage.py
Added function to generate API keys
Added "chisubmit-server initdb" subcommand

Will also seed database with an admin
Courses in the CLI are now lazy-loaded
Added beginnings of tests

Also modified session module to be able to use the
Flask test client instead of requests
Merge branch 'backend-refactor' into dev