Code refactoring and optimisations.

- Moved the game objects list to Game.cpp and made it into the base type GameObject instead of actors.

- Added a GetActors list in Game.cpp to go through the list of GameObjects and return only the actors.

- Removed small memory leaks all around.

- Removed the code in the Actor destructor because often an actor would be given a static char name and cannot be deleted.

- Added the code for the XmlSearchSyntax destructor.