0032042: Visualization, TKOpenGl - pre-multiply headlight flag into light source...

0032042: Visualization, TKOpenGl - pre-multiply headlight flag into light source position

OpenGl_ShaderManager::pushLightSourceState() now pre-multiplies headlight transformation.
Built-in shading GLSL programs have been updated to remove special handling if headlight flag;
also removed redundant pre-normalization of light source direction
(already normalized implicitly by Graphic3d_CLight interface).

Graphic3d_CLight::SetHeadlight() now raises exception in case of ambient light type.
OpenGl_ShaderManager::SetLastView() - removed unused property.