Add entities to world + basic desires for #27

Will try to submit my updates every night, since we're on opposite time zones. This adds the entities to the world (though they duplicate, will need to remove all on disable or something.) Also creates desires in JSON, though priority is unimplemented and it does not reassemble them from string class construction.

Example:
```json
"desires": [
      {
        "desireName": "DesireSwim",
        "priority": 0,
        "type": 4
      },
      {
        "desireName": "DesireLookRandomly",
        "priority": 0,
        "type": 3
      },
      {
        "desireName": "DesireLookAtNearest",
        "priority": 0,
        "type": 0
      }
```