NewLevelDialog now listens to the OK and Cancel buttons and sets the
dialogresult accordingly.
NewLevelDialog now has a public property for width and height.
Renamed Width and Height in NewLevelDialog to MapWidth and MapHeight to prevent
name clashing with Form.Width and Form.Height.
Added some comments for clarification.
MapWidth and MapHeight now have a minimum of 10 tiles and a maximum of 10000
tiles.
Reorganized the folder structure of the LevelEditor project.