Optimization of SpaceImpl.appToZ
Testing performance of removal when z-values are associated with many
spatial objects.
Changes resulting from integration with FoundationDB.

Decided that 0-height/width boxes are OK.
Overhaul of Region comparisons, which is fallout from Issue 3. The
comparisons at region boundaries were not always correct. Also, it
looks like the JTS/Region comparisons were just broken.

To address all of this, the concept of a grid -- the space in which
geophile works internally, has been strengthened. Comments in
SpaceImpl and in Region explain this. There has been some field and
method naming going along with this.

The major change is to avoid exposing Region.lo/hi values. These are
typically used in comparisons. These comparisons have to be done
carefully, with the equality cases being somewhat tricky. Instead,
comparison methods have been added, e.g. hiLE(int dimension, double
coord). Comments in these methods explain the logic.

These methods are used in the SpatialObject.compare(Region)
methods. One other problem fixed here, was that the comparisons were
being done in the grid space. They are now being done in the
application space, which should slightly decrease false positives.
Simplified Region constructor.

More testing of Region comparisons.
Little optimizations of Region. Informally, (timing mvn test), they
seem to make a big difference.
Tweaked comments in Region.
Comments, renaming, removal of some unused methods.