title: Export/Import entities which were created server-side
body: <p>If you create entity client-side through EntityManager.createEntity(), when exporting, breeze generates tempKeys and assigns them to newly created entities.</p>
  
  <p>But some entities are created server-side, but not saved(just created with new operator). Breezejs client is making a query. EntityState of fetched entities is Unchanged. PrimaryKey Id=0, it was just created, but not saved to db.
  When you make exportEntities on manager it does not generate tempKeys, and entity Id remains zero. I tried to manually set EntityState to Added on that entities before exporting, but still tempKeys are not generated.</p>
  
  <p>Any ideas how to properly export not-saved entity which came from server-side?</p>