A new command vbackground is created. Old background commands are made aliases for the newly created command (including vsetdefaultbg).
Tests are modified using newly added command vbackground.
Usage of QAGetPixelColor were checked and corrected.
Using simple comparison instead of regexp.
Improved usage of command vreadpixel for standard colors.
Command QAGetPixelColor was dropped from TKQADraw.
Procedures "checkcolor" and auxiliary "checkpoint" were moved to DrawResources/TestCommands.tcl
Some test cases using "checkcolor" for picking line color were simplified.
Procedures checkcolor and checkpoint were changed to handle situation when pixel is out of view.
Removed unnecessary use of command "vaspects -setwidth" in tests.
Revert -setwidth change in test bugs/vis/bug23525
