Graphics : Added position methods to DrawableElement. Code refactoring.
TowerDefense : Created Destructible class to be the parent class for all destructible elements.
Platform : Implemented new graphics API in Platform project.
Graphics : moved Background class from Graphics module to Implementation module.
Utils : renamed DrawingInfo to DrawingParam.
TowerDefense : Created a TileFactory and added tile backgrounds.
TowerDefense : Worked on tower auto-follow
TowerDefense : Updated unit classes.
TowerDefense : Implemented a better separation between GameMgr and Battleground.