Add an END specifiers to gamestate and order files

Game will now wait until the last line of an order file matches "END"
AI's MUST now finalise their order file with "END"

fixes #1

source/game/game.cpp

@@ -510,6 +510,7 @@ std::string CTTRTSGame::GetStateAsString() const
     state += '\n';
     state += GAME_HEADER_DELIMITER;
     state += units;
+    state += "END";
 
     return state;
 }