Fix subset so previous entity versions are skipped

The subset implemented for source dataset now includes all the entities from the subset, both latest and previous. This results in unwanted updates that will propagate to all receivers and can cause undesired effects. The subset feature should not have other versions than the latest. Optionally there could be a 

include_previous_versions_in_subsets

with default value: false

If this fix is not prioritized there should quickly come a warning in the portal that this is the current behavior for subsets - a note in the docs are easily missed.

ttps://support.sesam.io/hc/en-us/requests/7999?page=1