feat(schema, shared, api): move all types to shared, separate schema
 * schema is now stored in a separate crate to avoid dependency cycles
 * added note in README.md about handling unwraps

fix(api): timestamp -> timestamptz

feat(api): migration create_games

feat(api): migration create_actions

feat(api): migration create_gamedata

feat(api): migration create_users

feat(api): init diesel and db