Assets+, Grass Algorithm, proper State Switching.

Finally fixed a bug with state switching, where the list of event
handlers would dereference itself if an event handler switched states -
such as New Game. Fixed to allow delayed state switching at the end of
the beginning of a new game loop.

Implemented new tiles, such as bricks, wooden floors and grass.

Wrote grass-laying algorithm to aesthetically lay grass in gradual
clusters of weeds.