Move IdentityResult return value to IdentityTable classes?

[mcshaz]

At the moment the calls to the table classes (interacting with the database) return a boolean for a successful or unsuccessful create update and delete operations and the stores create fairly unhelpful IdentityErrors instance if the operation fails.

I would like to have the table classes in my own classes inheriting from these to be able to return more specific data about why the sql operation failed. The easiest way to do this is to move the returned IdentityResult on to the Table classes.

I have implemented this and can submit a pull request if you would like to see the diff.