Added TKOpenGlTest and TKD3DHostTest Draw Harness plugins.
TKOpenGlTest is automatically loaded by ViewerTest::ViewerInit().
Commands vgldebug, vvbo, vcaps and vuserdraw have been moved to TKOpenGlTest.
New command vglshaders lists GLSL programs defined by OpenGl_GraphicDriver,
previously implemented by "vshaderprog -list".
Added new command vdriver for graphic driver selection.
Removed erroneous code from command vstereo.
Now 'vcolorscale' command works correctly with the active view. Changed types of some variables from Standard_Real to Standard_Integer. Added options to set the width or the height of color scale explicitly. Test case is added.
