Geometry: MultiDrawArrays MultiDrawElements experiment

[einarf]

We should experiment with supporting MultiDrawArrays and MultiDrawElements in Geometry and see how that plays out. There are multiple concerns about these calls including how they will work with the "factory" aspect of the Geometry (vao factory) when rendering with many different shaders using all attributes or a full set.

We should make a worst case example in experimental or gl examples.

Report findings and code to Benjamin. Both projects benefits from this experiment.