Refactoring in preparation for integration with geophile. The goal was
to do the binding of the z-value in AbstractStore, instead of deeper
in PersistitIndexRowBuffer. This sets the stage for handling non-point
spatial objects which give rise to multiple z-values, each represented
by an index row.
Addressed review comments: Fixed imports, removed assertions, added
missing file header.
merge geophile: Refactoring in preparation for integration with geophile. The goal was

Merge pull request #1409 from geophile/sql-layer/geophile-integration
https://github.com/FoundationDB/sql-layer/pull/1409