OpenGL Real compatibility

In this merge request I have extracted changes necessary to ensure than OpenGL will work with Real type. When double is used, the arguments are passed directly, and all conversions are optimized away.

There were a couple of unnecessary functions, especially those accepting long double. It seems that @stranskyjan tried to get yade to work with long double? I suppose it eventually crashed when you tried to use minieigen? Well now this minieigen stuff works as from yade.minieigenHP import * in !383 (merged). But it took extra two months of work.

Also I have cleaned up a little the OpenGLWrapper and reformatted it.