Add a bb-code "editor" toolbar next to the textareas on the bbs thread and prod pages

Added some code to the end of script.js, and styles necessary for it to look good to style.css, for displaying a list of 'editor' buttons for bb-code to the right of the textarea on BBS and prod pages. This code is based on the 'Pouet bb-codeizer for winnars!' user script but refactored for slightly cleaner code, and formatting that better matches what already exists in script.js. It does not include the automatic 'by line' insertion code and other non-editor-essential code from the user script.

Requires images from http://asmcbain.net/projects/pouet.net/bb_editor.zip to be placed in a directory called bb_editor inside the gfx directory on the Pouet content subdomain.