Added CSS class to Circulate_css.ss, for freezing main window scrolling while modal is open;
class is applied and removed on expand modal shown/hidden events, via JS in header.php.

Added experimental code to articleTemplate.php and header.php, to scroll modal content to comments when appropriate;
there are issues with the coordinates of the content relative to the page, versus relative to the modal div.
Minor changes to experimental code to scroll to comments in modal.