0027058: AIS_ColorScale defines methods SetColor and SetWidth hiding inherited methods

0027058: AIS_ColorScale defines methods SetColor and SetWidth hiding inherited methods

Interface of AIS_ColorScale is revised to make it more consistent:

- Methods SetBgColor()/GetBGColor(), and corresponding field, are removed. It was used to select white or black color for the color bar frame (by contrast). That color can now be set explicitly by inherited method SetColor().
- Own methods Get/SetColor() are renamed to Get/SetIntervalColor(), to avoid confusion with inherited method SetColor()
- Methods Get/SetWidth() are renamed to Get/SetBreadth(), to avoid confusion with inherited method SetWidth()
- Method Get/Set for labels and colors, and DRAW command vcolorscale, now all accept index starting at 1
- Comments added to explain indexation rules