Random Worldgen

Added a random world generation function. A world will be generated
purely at random (cycles through all the tiles except the ones at the
border, and assigns either Forest (impassable) or grass (passable) to
the tile). It then runs a smoothing algorithm on the map to make it
appear less random.

When you load the applet, it will create a map. Press L to run a smooth
cycle, or N to make a new map. It will place the player entity onto a
randomly chosen empty tile.

There is no garantuee that all parts of the map will be connected, and I
have found no reliable way to make it connect them.