modified: SampleGameActivity, Character, Scene, SampleScene
added: ActiveObject, ValkyrieVF1A

changes:
	Character- change direction to 8 directions, implemented move(), 
				extended from ActiveObject instead of Object.
	Scene, SampleScene- modified addObjects(), constructor and camera 
						initialization.
	SampleSceneActivity- added ValkyrieVF1A as main character, 
							added onTouchEvent()(not work).
	ActiveObject- a subclass for objects with property isEnemy, 
					specifically for moving characters and bullets.
	ValkyrieVF1A- character implementation with 
					onDirectionChange() implemented.