Added support for TILE_SET_ACTOR
Added updateTile to interface.
Created interface IGetGrid
Added interface IGetTile
Tile now implements IGetTile
Since generics erases types, I had to add getIGetGrid so that the
clients than need a Grid can get what they need via getGrid in Scene.
Added getIGetGrid that returns the grid as an IGetGrid. See if this can
possibly be solved.
Grid now implements IGetGrid.
Added hasNoImage() to IGetActor interface.
Updated to use the new get interfaces.