Tag Titles + Menu & non-API thumbnail_count fix

* Swapped out parseInt for Number and updated the getVar function to support returning negatives and decimals as numbers.
* Added an option for reverting post page titles to the full list of tags.
* Moved the "BBB Settings" menu link to the upper menu due to the secondary menu missing on some pages (ex: http://danbooru.donmai.us/static/site_map) and breaking the script.
* Fixed the non-API thumbnail_count method so that pages with no thumbnails didn't break the script.