.clone() added to getBlockHash to avoid the chance of writing on sensitive data

[lsebrie]

When we introduce data on a Dataword it's by reference by default, so to avoid that a blockHash could be written by another class, a change is to introduced to return a copy of the Dataword

[colltoaction]

Makes sense if you don't want to add performance overhead to using DataWord.getData, but in the future we should evaluate the possibility of making it immutable.

[donequis]

DataWord should be a final class now that I think about it

[donequis]

@tinchou Making Dataword immutable will force us to alloc more memory when doing some operations with dispensable data. For example, if we have A and B on the stack and we want to add them, we can override A with A+B instead of creating a new object for A+B

[adauto82]

Seems to check out with the scope of the task.

[adauto82]

Check SonarQube