FLUID-5457, FLUID-5469: Remove FSS

Removed FSS. The fss directory in the prefs framework is still there and will be addressed by [FLUID-5482](http://issues.fluidproject.org/browse/FLUID-5482)
http://issues.fluidproject.org/browse/FLUID-5469

Also adds a fix for FLUID-5457, which allows for the cross to appear when using a custom default theme.
http://issues.fluidproject.org/browse/FLUID-5457
One extra dot at the start for this selector. Noticed this selector is not used anywhere in infusion. Is it here for future?