Migration to ember-data 1.0 beta7

As long as ember-data 1.0 brings many breaking changes, there's a lot of things to check...

[ ] invoicesPending must be well sorted 
[ ] invoicesOverdue must be well sorted 
[ ] invoicesPaid must be well sorted 

[ ] quotationsPending must be well sorted 
[ ] quotationsFailed must be well sorted 
[ ] quotationsSucceeded must be well sorted 

[ ] purchaseOrdersPending must be well sorted 
[ ] purchaseOrdersSucceeded must be well sorted 

[ ] items must be well sorted