Configure full vs. summary for indexes, feeds. Closes #3, #4.

Also update example project .frogc and blog post.

Related: Syntax highlighting (if pygmentize is provided) is _always_
done for index pages (both full and summary), and _never_ done for
Atom feeds (neither full nor summary).

Rationale: Always want that appearance for the web site. Never can
guarantee it in the feed, so use the reliable (and smaller) plain
<pre> formatting.