Demo3 now draws 2 squares in different locations

Demonstrates the model/view matrix
Moving out of the dark ages with glDrawArrays
Added OpenGLDemo4, showing glDrawArrays

Need to revert changes to OpenGLDemo3
Revert "Moving out of the dark ages with glDrawArrays"

This reverts commit f0859699fdf3586e545ad52b6a2e488d7602e3e5.
This change should have gone into Demo4, not Demo3
Added / Fixed comments