.flex-control-nav class/CSS interferes with WooCommerce gallery

[JiveDig]

It seems Woo core thumbnail galleries and GRS both use the .flex-control-nav class. GRS sets the z-index to 100 which causes some conflict with other elements in Woo product galleries.

z-index is obviously not horrible breaking, but it's still not great.

I would be worth setting the lowest possible z-index to still allow GRS to work IMO.