Cleanup and fixes.

Discovered that sidebar.php was injecting $_GET[] variables directly into its javascript; wrapped those with json_encode().  Wrapped other js injections in add.php and update.php as well.  Not sure if this fully closes XSS vulnerabilities, but it has to help.

Altered item_tag_table queries to not throw constraint violations on duplicate inserts.

Removed unused user_id parameters from fof_db_get_tag_by_name and fof_db_create_tag.

Quieted more warnings, normalized more indentation.

Replaced font elements with spans in emitted html.

Rearranged fof_subscribe() to be less confusing/repetitive.

Removed several wrapper functions from fof-main.php which simply returned the fof_db_* functions, exempli gratia fof_get_users().

Diddled with add.php and update.php, trying to get outputs prettier and more dynamic.  Not yet completed, so it's even messier than it was, for the time being.. (TODO)