Roadmap: beta-1.0.0

[ewen-lbh]

This is the roadmap for schoolsyst's first "official" release: beta-1.0.0 !

• [x] README.md
• [ ] move api.schoolsyst.com/api to /
• [ ] move api.schoolsyst.com/admin to admin.schoolsyst.com
• [x] basics of www.schoolsyst.com
• [x] move from sqlite3 to postgresql
• [x] put django secret key in env variable
• [x] CORS: only allow *schoolsyst.com
• [ ] email verification for account registration
• [ ] Store settings on the user and get rid of settings-definitions
• [ ] Switch to a flexible year division strategy (see schoolsyst/frontend#48)
• [ ] Add updated_at and completed_at fields for all resources
• [ ] Introduce /quizzes/
• [ ] Add mongodb-like ?filter, ?sort, etc. (see https://docs.python-eve.org/en/stable/features.html#filtering)

[ewen-lbh]

Note that security-related changes are not critical enough to perform an attack: I wouldn't put them here publicly if they were. eg. for now, api.schoolsyst.com's CORS header do not accept anything, and the secret key, although still hard-coded, is not the one in this repo