It reads the specified XML level file and 
loads it the same way the event parser would.

- It clears the LevelData object. (if it exists)
- It erases the map_mc movieClip. (if it exists)
- It converts the XML data into flash variables, which are stored in the "LevelData" object.
- It creates a map_mc movieClip.
- map_mc sets itself up based on the LevelData.