Move popup arrow size-related CSS to theme

[gabrielschulhof]

The portions of the popup arrow CSS that deal with the size/offset of things need to be moved to the theme file, because the size of the popup arrow /should/ be customizable (hopefully via TR).

[jaspermdegroot]

@gabrielschulhof

I don't agree. All size and position related CSS is in the structure CSS files. There shouldn't be any widget specific rules in the theme CSS. If you have custom build and don't use popup (arrow) you don't want rules for that in your CSS.

I think it would be cool to add a page to the demo center where you can change popup arrow CSS with range inputs and directly see the result. Then you can change the values in your own build or add overrides.

[gabrielschulhof]

d08b0cb fixes this.