1. We won't change their semantics -- they'll work as they did before: either bounded or toroidal.
2. They'll be officially deprecated.
3. New versions will have, instead of a "toroidal" boolean parameter, the following new parameters:

	- mode:	one of Grid2D.BOUNDED, Grid2D.UNBOUNDED, or Grid2D.TOROIDAL
	- includeOrigin (a boolean), which indicates whether to include the origin point itself in the neighborhood

4. Eventually we may push more functionality up into AbstractGrid2D to reduce the enormous amount of code replication,
but that's for later.

I've got versions of this code done, completely untested, for the 2D grids.  Want to do some testing first before
translating them to the 3D grids.  Then eventually will get them out on SVN.