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.

I thought about that, but for the bug fix it doesn't matter which service path or tenant that is used, so I removed that part to have the test 'cleaner'. The bug just happened to be found using a call with a service path, that's all.