OpenGl immediate mode - get rid from GL display lists
Visual3d_TransientManager, Graphic3d_GraphicDriver:
removed outdated unused methods to draw primitives in immediate mode.
New Draw Harness command to swith rendering mode in immediate mode.
When set to false scene will be always redrawn in back buffer.
V3d_View::ToPixMap - temporarily switch immediate mode to draw into back buffer
Make happy immediate mode dump on OpenGL without FBO (like ms software implementation).
OpenGl_Workspace::RedrawImmediatMode - invalidate back buffer when immediate mode drawn into it
Added more detailed description for Graphic3d_GraphicDriver::SetImmediateModeDrawToFront method
Adding of test case
