feed: Convert 'friendly-name' setting to 'name-format'

feed: Convert 'friendly-name' setting to 'name-format'

In Debian bug 722009, Joey Hess wrote about the 2.x series [1]:
> The current From line generated by r2e is From: Blog: Author
>   where
>     Blog is the name of the blog, or some page like a wiki's RecentChanges
>     Author is the author of a post
>       iff the blog sets that info in the feed
>
> In mutt the Blog part often occupies the whole displayed Subject field,
> which is fixed width. So the Author cannot be seen. This is particularly
> a problem with planets, where the author of a post matters a lot.
> But also with some blogs that have multiple authors.
>
> For these sorts of blogs, I would generally prefer to use a From line
> like From: Author (Blog)
> This does mean that when sorting by author, all posts of a blog or
> planet feed may not appear together, but that would be an acceptable
> tradeoff to me.
>
> One way to implement this (other than just changing the format string)
> would be to make OVERRIDE_FROM able to contain a format string,
> so it could be configured on a per-feed basis.

The new setup makes the name-formatting configurable on a per feed
basis (what Joey wanted), but it's not without side effects.  For
feeds where some information is missing (feed-title, author, or
publisher), we used to adjust the formatting on the fly.  For example,
you'd get output like '{author}' if the feed-title was missing,
instead of getting ': {author}'.  Now users bothered by this will have
to manually override the format template for feeds missing crucial
data.

[1]: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=722009

Signed-off-by: W. Trevor King <wking@tremily.us>