Make the engine "easy" to build by using CMake instead of a simple VS Solution

[Ybalrid]

There's some things that have to be done for this to works, taking inspiration on how Ogre does things:

• [x] Properly package and maintain the "Annwvyn SDK" (dependency package) and use that environement variable to find the dependencies, so that this repository can actually be usefull. (I could even put that on GitHub, everything is freely redistribuable. Some are allready on GitHub and can be integrated as submodules)
• [x] Write a CMake script that takes the location of the Annwvyn SDK and output all the includes and libraries configuration for building Annwvyn via a package. This would be callable via something like find_package(AnnwvynDeps REQUIRED)
• [ ] Reorganise the source code in the same way the filters are inside Visual Studio for clarity
• [ ] Write a CMakeScript that permit a client application to directly include Annwvyn and all buid libraries via a find_package(Annwvyn REQUIRED)

Here's the listing of all the libraries used from Annwvyn's Wiki

OVR the Oculus Virtual Reality API
OpenVR the Open Virtual Reality library from Valve, powering the HTC Vive, among other hardware
Ogre 3D The Object-Oriented Graphical Rendering Engine, a Free/Open-Source 3D graphics library, in version 2.1
Bullet Physics A physics simulation and collision detection library
OpenAL-soft a Free implementation of the Open Audio Library originally developed by Creative Labs.
libsndfile Lib Sound File, a free sound file decoding/encoding library that support many format (but not the copyrighted MP3)
ChaiScript A super cool scripting language in C++ for C++
GLFW GL FrameWork, a library to help develop OpenGL application. Used for window and OpenGL context creation after Annwvyn 0.3.X using Ogre 2.1
BtOgre21, my personal fork of BtOgre, adapted for Ogre 2.1. presentation of the original one here
TinyXML2 A small (2 files) object oriented library to import/export XML DOM

[Ybalrid]

the situation si good enough for now