Added methods to add and remove Gridables in TileGrids.
Added clarification to UnSizedGridable interface documentation.
Revised AbstractGridDecot and AbstractDecor classes.
Removed equals and hashcode methods from AbstractTileGrid - too slow.
Gridables shouldn't implement equals and hash methods.
Duplicated getContainers method but with the explicit fields.
Made the coding of extensions of AbstractEntity easier.
Clarified TileGrid interface.
Dramatically improved AbstractGridEntity - now interacts with tiles.