Allow instantiating a new Model object with a UUID already populated.
Allow instantiating a new Model object with a UUID already populated.

 There was a minor bug with the save logic where it was ignoring the UUID for new models.
 This is rather a-typical behaviour anyway, as most models with a UUID get it generated automatically.

nicholasryan/CorePlus,nicholasryan/CorePlus,nicholasryan/CorePlus,nicholasryan/CorePlus,nicholasryan/CorePlus,nicholasryan/CorePlus,nicholasryan/CorePlus,nicholasryan/CorePlus