import Bullet source code from github.com/bulletphysics/bullet3 under bullet/src folder
(using 'src' folder from master branch, hash 5ed49cc3a24626bb17da5c69cc8cb758f81e91e4)
Create README.md
Update README.md
Replace enet with raknet, initial project structure

RakNet is MIT-licensed now, and is a better, more complete fit for the
engine.
Initial work on a OgreKitServerCore