Evaluates wheter this GridSet is different enough from
another so that if this
GridSet were replaced by
another all layers referencing this GridSet should be
truncated.
The rule is, if any of the following properties differ:
#getBounds(),
#isTopLeftAligned(),
#getTileHeight(),
#getTileWidth(),
#getSrs(),
OR none of the previously mentiond properties differ and
#getGridLevels() are
different, except if both the grids of
another are a superset of the grids of this
gridset (i.e. they are all the same but
another just has more zoom levels}.