Return version with all statement

[Leobouloc]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.
As pointed out by @SergioSim in this comment , the xAPI spec requires that statements be returned with the API version:

Statements returned by an LRS MUST retain the version they are accepted with. If they lack a version, the version MUST be set to 1.0.0.

This is currently not the case