Added a sprite for a leader
Added a few background images for testing. grass.png is extremely ugly,
greenborder and smokyback less so.
Rearranged things so that the guys moving around randomly are Wanderers
and added a Leader. Leader and Wanderer both extend Entity. 
Instead of moving the camera, the arrow keys now move the leader around
The camera follows the leader.
Ran into an issue where the centercamera function was for some reason
letting me pan 10 pixels past the edge of the map to the south and east.
Added a quick fix for this, but it's ugly and I need to find the root
cause.
GameMaps can now be created by simply constructing them with a
BufferedImage to use as a background.
Missed a few files in my last commit.