Persistence update!

Player data persistency has been implemented, so all player/account data now persists over server restarts.

Now that the backend supports most of the features I want, I'll finally get to work on the actual "game" part of this project. This will be an iterative process, with new features added every once in a while.

Technical info:
All player data is now stored in a local, containerized database, in which all confidential data is encrypted. For example, account credentials are encrypted with bcrypt and salted.