Use email instead of username for account logins

The code gets confusing pretty quickly when you call .username on an
object and actually get back an email address. Since
passport-local-mongoose allows the value to be configured, it makes
sense to take advantage of that.
Add name field to registration pages

The name field will make it easier to refer to other users rather than
having to use their email address all the time.
WIP: Simplify admin app