makeBgBlack/WhiteSpt() top.js in scripts.js does bkg and fixes bkg for all echos & scale!

To change the initial background color:

1. Change it in view1spt in scripts.js

2. Change initial button position up/down in
makeToggleButton() call in controls.js (used by all control panels).

3. Change initial
toggleIsDown[backgroundIndex] value in jcontrol.js
(this also affects color of echos)

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CONTROLS.JS:
makeToggleButton("bgWhiteSpt", "bgBlackSpt", ...

makeEchoPDBIdSpt() in scripts.js uses getEchoColor() in scripts.js
which polls toggleIsDown[backgroundIndex].

In a view script, include a background command,
then in doViewLink() in jcontrol.js, force the button as appropriate.

setButtonState("up", backgroundIndex);