Untested: Create a Thing, linked to an existing Location

[hylkevds]

I just ran into a bug in our implementation and noticed something that is not tested yet:
Creating a Thing and directly linking to an existing Location:

{
  "name" : "S311",
  "description" : "Room S311",
  "Locations": [
    {"@iot.id": 1}
  ]
}

Similarly, Creating a Location and directly linking to a Thing is also not tested yet.