Create new script containing references to commonly accessed elements

This makes it easier to change/update these common variables, as it only
needs changing in the HTML, CSS, and here, and all references will be
good. Minified version pending.

Also updated a class and ID (both of which are in the new list).
Update core script to take advantage of new variables access
IE9: Remove workaround for New Window SVG added in 7160f16

I finally figured out what is going on. Back to the original SVG!
:smiley: Also applied same fix to Gear.svg

And added missing HTML update for last two commits.