review referencing factories and transform builders

1. The old EPSG factories design (thread-safe through blocking synchronized statements) has been replaced by concurrent EPSG factories, thanks to Refraction work. However the old implementations have not yet been deleted.
2. We need to review the classes, make sure that they can do the same work than the old implementation
3. Delete the old ones.
4. The math transform builders are new classes. They need to be reviewed as well.

This technical debt (ie waiting for martin to reveiwed has stalled out). As such we can probably just proceed to make the transition.