Move map generators to separate executables

[ElnuDev]

Moving each map generator (box, corridors, etc.) into a separate executable and then calling them from the main application instead of having them hard-coded in would increase customization potential for players, who could then create their own map generators for the game.

[ElnuDev]

Going to close this for now, might change my mind and decide to do this later but it's not a priority.