0025783: Visualization - allow Z-layer to draw 2D objects and to make it alternative...

0025783: Visualization - allow Z-layer to draw 2D objects and to make it alternative to Overlay and Underlay

Add one more pre-defined Z-layer Graphic3d_ZLayerId_BotOSD.

Define new Transformation Persistence flags Graphic3d_TMF_2d and Graphic3d_TMF_2d_IsTopDown
for displaying objects in screen coordinates.
Anchor point defines angle of the screen to display the object in similar way as for Graphic3d_TMF_TriedronPers.

Extend Draw Harness command vdisplay with new options:
 -overlay as alias for -toposd.
 -underlay and -botosd.
 -noselect to prevent automatic selection activation.
 -dispMode and -highMode to define displaying and highlighting modes.
 -2d, -2dtopdown and -3d to manage displaying in screen coordinates.
 -trsfPers and -trsfPersPos for Transformation Persistence options.

Drop command vsettransmode, replaced by vdisplay.

Correction of test-case bugs vis bug641