Diffing_Engine: see if parallelization can improve performance

#### Description:

- Surely can help the `SetHashFragment` part - already tested: up to 50% reduction in time when building a Revision (parallelising only when dealing with large collections: >=1000 objects)
- Have a go with swapping `DifferentProperties` with a custom function ([example](https://stackoverflow.com/questions/4951233/compare-two-objects-and-find-the-differences)).