Create some classes to store the mesh data streams and adapt the import
file accordingly.
Add object and camera classes to be manipulated by the game.
Render the meshes in the graph scene using only position vertex stream
and an unicolor shader.
Also add some models and a startup package to ease testing.
regroup opengl version and window creation and event polling in the
viewport file.
To further clean up the files layout, move input.lisp to engine folder
gl-utils is now used for some simple macros
