Add a middle name field

[bemoody]

The "first and middle names" field is confusing to authors. (It doesn't look like anybody so far has actually used that field the way it was intended.)

Also, when we automatically generate emails for credentialing, it's better to write "Dear Firstname", not "Dear Firstname Middlename".

We should encourage authors to include their middle names or middle initials, since it can reduce ambiguity in citations (and it also arguably looks more professional.) I think the best way to do this is to have separate fields for "first name(s)" and "middle name(s)".

We should display authors' names in the project byline the way they want them to be displayed, but probably should default to displaying first name(s) plus middle initial(s).

We should have a common style for initials in the byline. Assuming that we're going to stick with APA style for the suggested citation (which AFAIK requires dots after initials), I'd suggest we do the same for initials in the byline.

Regardless of whether the author's name is displayed in full or as an initial, we should probably require them to enter their full name for citation metadata purposes.