GTK 3.12 Compliant icon names

rename all icons to match new gtk icon naming convention

There were a few icons that don't exist anymore for us, such as 'gtk-yes', 'gtk-no', and a few others.
I tried to find appropriate replacements, but this will probably need more tweaking in the future.
In the mean time I hope this alleviates some crashing due to bad icon names that others have reported downstream