Video Settings UI Improvements and A New Lighting Setting

Added an option that allows light contribution to be clamped to (1,1,1),... effectively reducing oversaturation.

Added a lot more video options (currently all under experimental/high end since impact is unknown).
When debugging is enabled for rendering, an OpenGL debug context is created and a debug hook is registered. This logs a lot of info from the graphics driver in the log.

For video settings see issue #962