Utils for texture & main loop + Back ends examples

To see the examples using the WebGL back end, use the command:
sbt "backendExamplesWebgl/optimizeJS"
and open the file backend-examples-webgl/index.html with your favourite web browser

To use the LWJGL back end, use the command:
sbt "backendExamplesLwjgl/run 2"
(you can replace 2 the number of the example you want to see, between 1 and 5 for now)

Note that the example 5 "render-to-texture" require OpenGL 3.0. So if you use a Intel IGP older than a Sandy Bridge, LWJGL will probably refuse to create the context (but we had it working with an Arrandale when using Linux 3.11 and a OpenGL 2.1 context, it's just not very elegeant)