AIS_TextLabel - new public class to display simple text labels (based on MyTextClass private class from Draw Harness).
ViewerTest::Display() - add more reliable replacement for VDisplayAISObject() with no viewer update flag.
vdrawtext command redesign:
- Use new AIS_TextLabel class instead of private MyTextClass.
- Take object name and allow to clear labels from the Viewer.
- Use parameter name + parameter value syntax instead of strict list of mandatory arguments.
- Use [0; 1] range for colors and accept names.
- Drop redundant argument "isMultiByte".
- Support argument -noupdate to skip Viewer update.
Update test cases to new syntax of vdrawtext.
Make vcamera command syntax more clear.
Restore command vraytrace as alias to vrenderparams.
Replace occurencies of atof() by Draw::Atof() in ViewerTest_ViewerCommands.cxx.
OpenGl_GraphicDriver::Redraw() - do not recompute structures more than required
OpenGl_Workspace::Raytrace() - bind proper FBO before clearing it
Visual3d_View::Redraw() - perform automatic 2nd redraw on device lost
