Updated earth map.
Distinguished EditScreen from GameScreen.

The EditScreen is for map editing;
the GameScreen is for playing the game.
Made GameScreen listen to mouse actions on its map pane.
Added empty LogPanel to GameScreen.
Showed open file in LogPane.
Allowed time-lapse in LogPane of history.
Start civ on land.  Game defaults to Earth without bonuses.
Choose first civ site; randomly add bonuses; store mines.
Play game with just one city.
Sorted methods in 'Civilization'.
Sorted methods in 'GameScreen'.
Can play game with 1 village, and get final score.
Test that first location and first farm are adequately located.
AI can build villages across Eurasia.
Populated tech tree.
Chooses tech to research.
Initialized improvements.  Build some improvements.
AI can explore and settle Afroeurasia.
Calculate non-boolean effects of wonders.
Define all units.  Test that settler's UnitType.isSettler .