Add AkGeometry type as a marker for runtime-only JTS Geometry objects.

Includes two simple functions:
- GeoWKT wraps WKTReader as a way to get a Geometry instantiated
- GeoTypeString wraps the getGeometryType()

Minor exception tweaking for message propagation.
merge nathanlws: Add AkGeometry type and GEO_WKT, GEO_TYPE_STRING functions

Merge pull request #1596 from nathanlws/sql-layer/akgeometry-type
https://github.com/FoundationDB/sql-layer/pull/1596