Added a test horse to lane one
Increased the Horses Y deadzone
Fixed sprites appearing further down

By taking into account the X and Y dead zone of the sprites frame,
sprites now appear in position closer to the one specified on creation.
Added second lane of horses
Set Sprites default direction to North
Added the option to center the sprite
Added Wagons to the third lane
Attempted to resolve mysterious memory leak
Modified Form
Fixed memory leak

It was caused by the SpriteSheet class rapidly creating Bitmaps and
Graphics objects. Solved by declaring them as class objects and having
the graphics object clear the bitmap each time