groups with line breaks in the description break group listing display

group descriptions are stored in plain text (no html), which means line breaks (\r\n) are used instead of html <br /> tags. the line breaks affect the new manage groups listing display (the presence of a group with a line break prevents the list from displaying).

we need to convert at some point in the process. I handled it in Group/Page/AJAX.php, just before we JSON encode, by a simple str_replace on the description field. but it might be better to handle it directly in Utils/JSON.php so that we ensure there are never any line breaks in the data.

reproducible on sandbox:
http://sandbox.drupal.civicrm.org/civicrm/group?reset=1