Fix issue #246 Problem with requireAccountVerification and IsAccountVerified 

In order to solve the #246 issue,

The user creation problem:
The problem was if you change the requireAccountVerification from false to true,
* All accounts created before the change won't be able to login.

The second problem was
* If an email was supplied the AccountVerification was mandatory.

The login problem:
The test for IsAccountVerified is only relevant if we were asking for requireAccountVerification

Now, when a user is created, we check for the requireAccountVerification and set IsAccountVerified to the right value. And If an email is supplied we send a confirmation email.

During authentication we only go throught the test on IsAccountVerified if RequireAccountVerification is needed.