Obtaining a copy of the wiki + Old bullet manual source

[cuppajoeman]

As I mentioned here: #4557 I'm hoping to improve the organization of the bullet knowledge base.

My goal is to condense all of the knowledge we currently have into doxygen documentation so that we link directly to source code in the documentation and keep things portable.

Towards this goal, I've heard that there used to be a wiki and was wondering if @erwincoumans or whoever was hosting that wiki has any snapshots of it so that we can pull information out of it and re-use it so that we don't have to re-write a lot of the content.

Also the bullet physics manual: https://raw.githubusercontent.com/bulletphysics/bullet3/92a34440762ab94aec1ee766ef41b176ab7b6ef7/docs/Bullet_User_Manual.pdf has some assets in it that are vectorized, and moving information from pdf to doxygen is hard without the original document. So I was also curious if anyone has the source document used to generate the pdf for the manual.

Thanks