Changed default registration form to require a unique email. ref: 8c31489d37ae98770b8642164d5c78c3f0ed040e
Extended the user authentication form to prompt a user for either username or email instead of just username. ref: 3c28806fd4d2cc2269480b9178f39f9198737e44
Updated the username or email form to have a better error message on failure. ref: f9b94ef615a3c21159884dca22c26dd93f2cca7f