[Greasemonkey] where is GM_set/getValues stored

[Bill Donnelly]

fyi: which is why pref entries cannot be dynamically removed, because
the prefs.js is a plain-text file that is re-written when you close Ffx, so
that is the method they chose.
it would have been nice, tho, if they would have made them "invisible" once
they are reset/deleted, so that it looks like they are really gone, to 
the user
and any programs, for the duration, until Ffx is closed.