Added three js and removed lightgl.js

I have removed the dependency of lightgl.js with three.js. Please see the demo in ``Threejsdemo.html``. I have hard coded some color or int values in the code which can be changed. 
I have added a new version of the openjscad.js as OpenJsCADWithThreeJS.js which has the support for three.js . I haven't deleted anything, wanted to talk to you guys first.
I had to use the previous version of ThreeCSG.js as they have change their code base and thus, the latest version is no longer a wrapper for CSG.js . Also, ThreeCSG.js was outdated as Three.js is changed a lot since 2011. So, I modified it too. Thus, the ThreeCSG.js which we are using here is custom and now can be treated as a standalone library too.
I think that we should create the directory structure too like different folder for ``examples`` and ``src``. I can include those changes in this PR itself but wanted to know what you guys think. 
So, here the delivery as promised :)