[Part 1][Part 2][Part 3][Part 3.5][Part 4][Part 4.5] The Firefox Add-ons site, particularly the extensions side is undergoing a major overhaul this weekend. “Mozilla Corp. will relaunch its popular Firefox add-on site Monday by culling the several thousand extensions listed for its open-source browser to just a couple of hundred. Rather than list all the available Firefox and Thunderbird extensions — Shaver estimated that there are approximately 2,000 available now — the site will drop marginal add-ons, as well as those no longer maintained by their creator or not updated for the browsers and e-mail clients now in use. A couple…