Java: Generate a hashCode method for all FObjects.
Java: Generate a hashCode method for all FObjects.

Fixes #1021

foam-framework/foam2,foam-framework/foam2,foam-framework/foam2,jacksonic/vjlofvhjfgm,jacksonic/vjlofvhjfgm,foam-framework/foam2,jacksonic/vjlofvhjfgm,foam-framework/foam2