Add "noindex" to Atom and RSS feeds

[ebellempire]

I have a client who found that relatively obscure atom feeds (e.g. for specific tags) had been indexed strongly in Google. I updated their theme to selectively add the <meta name="robots" content="noindex, follow"> directive for various kinds of generated content, but of course the theme does not come into play for output formats like Atom and RSS. Adding something like the following to some of the item output formats would probably be universally beneficial in terms of SEO. I cannot think of any drawbacks.

<?php // updated version of browse.rss2.php
header('X-Robots-Tag: noindex, follow');
$convert = new Output_ItemRss2;
echo $convert->render($items);

I can make a pull request if that's helpful. If so, I would request some guidance/input regarding single item output formats (as opposed to item browse), as well as how to handle Omeka XML and RDF. I assume those should also not be indexed, but maybe there's a reason someone might want to leave those alone?