Is your feature request related to a problem? Please describe.
Using EmailAddress introduces more queries, and not all applications want to deal with a user having multiple email addresses.

Describe the solution you'd like
Introduce a new setting; setting.ACCOUNT_USER_EMAIL, if it's true it will use the user email instead of EmailAddress when checking any authentication or similar related to email. By default this option would be false.

Tangentially related to #284