0029290: Visualization, TKOpenGl - allow defining Light source per ZLayer

Graphic3d_CLight is now defined as a class inheriting Standard_Transient,
so that it's fields now should be accessed through methods.
Graphic3d_CLight::IsEnabled() - new property allowing to disable light source everywhere.
Confusing alias OpenGl_Light has been removed.

Graphic3d_CLight::SetAttenuation() - the upper limit 1.0 of attenuation factors has been removed
since it contradicts to OpenGL specs and does not make sense.

Graphic3d_ZLayerSettings::Lights() - light sources list is now property of ZLayer.
When defined, it overrides light sources defined for View/Viewer.
New class Graphic3d_LightSet has been defined to define a set of light sources.

V3d_Light - removed obsolete interface for debug drawing lights sources.
V3d_Light is now an alias to Graphic3d_CLight.
V3d_TypeOfLight is now defined as a typedef to Graphic3d_TypeOfLightSource.

src/StdPrs/StdPrs_Plane.cxx

@@ -24,7 +24,6 @@
 #include <Graphic3d_ArrayOfPolylines.hxx>
 #include <Graphic3d_ArrayOfSegments.hxx>
 #include <Graphic3d_Group.hxx>
-#include <Graphic3d_Vertex.hxx>
 #include <Prs3d.hxx>
 #include <Prs3d_Arrow.hxx>
 #include <Prs3d_ArrowAspect.hxx>