调整world形状，正确比例显示box2d调试图形
#	modified:   Classes/Box2dLayer.cpp
#	modified:   Classes/Box2dLayer.h
#	modified:   Classes/Box2dPhysicsSprite.h
#	modified:   Classes/GLES-Render.cpp
#	modified:   Classes/GLES-Render.h
#	new file:   Classes/GravityBallConfig.h
#	modified:   Classes/HelloWorldScene.cpp
#	modified:   proj.win32/GravityBall.win32.vcxproj
#	modified:   proj.win32/GravityBall.win32.vcxproj.filters