Completed ATMO-375 and ATMO-384

* New Migrations remove ProviderSize (Deprecated)
* Add 'Size' key to InstanceStatusHistory
* Check for size on 'update_history'
* Call 'update_history' on every convert_esh_instance
* Lookup Size/Machine before converting if they are of type Mock*
Merge branch 'ATMO-375' into abyssinian-nightjar