World persistence model

[CansecoDev]

Design a world persistence model that allows for world persistence, spawning entities on map load and saving them on certain critical events like a map change or previous to a server shut down.

[CansecoDev]

A basic implementation should looks like this.

• Need some way to tell the engine that a map is a "world", fastest way should be a single text file worlds.txt with the name of every map that has persistence separated by line.
• Those worlds should override g_raceMode to 0 to avoid problems.
• New column with player world x y z for player position persistence.
• Account (being logged) is mandatory to join the game on these maps.