refactor keyboardNav.addFocusBGColor, .addFocusBorder from .beforeLoad
move keyboardNav.options/focusBorder near focusBorderNight
keyboardNav.options.focusAddBGColor and .focusAddBorder

options to disable the background color and border highlight, because keyboard nav is still plenty useful even if highlighting is partially/completed disabled
clarify "for night mode" in keyboardNav.options.focusBorderNight
whoops wrong option
rename .focusAddBGColor/.focusAddBorder to .addFocusBGColor/.addFocusBorder
Merge pull request #1539 from andytuba/keynav-addfocus-options

keyNavigation options to disable background/border