Updating NGL Demos

Been updating some of the demo code I use for this years lectures been quite useful doing the Python and C++ API at the same time as it's highlighted a few bugs in the system and I've cleaned up a load of silly C++ code that makes no real sense in the Python implementation.

Been finding prototype in Python quite quick and when I transfer from one system to the other it's actually fairly quick (usually just changing -> to . and the odd ::)

Managed to do two demos so far one for Lighting and one showing how the primitives work, going to do the spotlight next

Here's a couple of images