Add email to author, in addition to name

Convert the name string to an author struct, adding the email string.
Allow showing the email, instead of the name (add it to the toggle).
Allow showing only the username of the email

Add an additional author display mode, showing the user name and not the
domain name. Left to do is a "conversion file", for emails to usernames.
Identical to what git cvsimport uses, just used in the other direction.