fixed a bug in POST /v1/contextEntities

### Description
The type of the entity was not passed to the lower layers and thus not saved in the database.
It was lost.  The fix was more than easy, but as the case was not covered in functests, a new functest had to be added.

Fixes issue #684.

This PR solves an existing bug in previous version (0.17.0)? In that case, a line in CHANGES_NEXT_RELEASE is missing.