Field `_entityIdentity` isn't needed?

Hi Tony,

Back to our old discussion https://trackable.codeplex.com/discussions/554515. I just removed any handling of `_entityIdentity` field and it still passes all tests. My application also works fine. Maybe some of your TE-based apps will fail. If so then it would at least be worth adding another unit test to depict the real need for `_entityIdentity`, but so far my feeling is telling me it is exactly one field too much for the task.

Please review and if this attempt incurs no other problems, then the T4 templates and sample apps must also be cleaned up (here I would count of your help).

Thanks,
AZ